People who have not been at it for long often obsess over lifting (or other activities) way too much if you ask me... Especially with the wrong stuff... They don't realize that this is ultimately a reasonably simple endeavor (not easy) that does not have to consume your entire timetable. If it weren't for T-Nation, I would spend anywhere from 3 to 5 hours per week thinking about lifting (i.e. while I'm in the gym...).
Plus a couple hours of food prep on sunday.
The important thing is to give it your all while you are under the bar. And then forget about training until it's time to lift again (just making sure you get to chance to do that too, of course).
And I am overall a fairly serious guy when it comes to training. My approach will have to change if I want to compete in BBing (PL competition would be far easier in that aspect as no crazy 3 month dieting is necessary), but just being a very big and strong guy is entirely doable this way. There are many guys who lift despite being a fireman or ER nurse or someone who travels a lot like some geologists or soldiers or whatever.
Investment bankers just starting out on the other hand are people who have a real excuse (but then again, their lifestyle is not one for people who care about their health and/or physique).
There are many ways to make a strength training diet fit in with your life... You'll just have to use your head here. Prepare most of your meals on sunday or so, use a vacuum-sealing machine - or whatever they're called in English - to keep it fresh for the week, or maybe 5 days or whatever.
Works great with steak etc, not so much chicken imo (but I hate chicken anyway).
This cuts down on food prep time etc in a MAJOR way. Keep powder in your shake bottles, put them in the car or backpack or whatever, plus bottled water (I can't stand tap water in most areas I travel to, but maybe you do I don't know...) and then just mix whenever you need a meal.
My wife cooks whenever she feels like it (and she cooks whatever she wants, usually something special we don't usually eat, certainly not BB food). So maybe a few times per week.
I would never want her to spend all day cooking and cleaning like my mother used to... Poor woman... Cooking every meal right before you eat it is one hell of a waste of time.
You can be flexible with your food choices. You're not doing BB contest prep after all. You do not need to eat the exact same food every day.
Pick your favorite/most available foods, and just try to eat a fat or carb source with a protein source if possible. It's quite easy actually (ignore what carbs there are in fat sources or what fat there is in most carb sources). Pizza can be fine too. I like some fish oil or cod liver oil or whatever with carbs or mixed stuff like pizza though (health). I eat pizza virtually every day, sometimes more than one.
I've posted training splits for people with ever-changing schedules before. It's actually not that difficult to come up with something as long as you don't access to weights, and then there's still bodyweight stuff to hold you over (although there are gyms almost everywhere).
Do not do long duration steady state cardio for an hour or more. Just do a session or two of HIIT per week, or fasted AM low-int cardio for 30 mins after waking up 3-4 times a week or so. Only necessary if you lead a sedentary life-style though, imo. If you are active due to your profession, then you may as well ditch extra cardio completely unless your endurance is really bad for example.
If you really want to get somewhere in training (that is, in your case, good strength levels) then you'll just have to make things happen. Inform yourself about available gyms in areas you travel to, have a basic understanding of how much protein and how many cals there are in an average portion of the foods you usually end up eating (not too difficult).
You don't need to eat 6 times a day either, especially if you can get in enough food in fewer meals or if you don't want to gain weight.
Missing family reunions because of lifting is ridiculous unless we're talking multi-week trips. If it's just a day or two, even if it happens relatively often, it ought to be doable.
Same for birthday parties late at night/early in the morning. Personally I need to keep my sleeping schedule consistent, but that's just because I already suffer from insomnia and can't sleep at all if I don't do things a certain way.
How much sleep you need also varies greatly from person to person, food intake and supplementation, hell, even what you sleep on I guess/stuff that influences sleep quality.
I got through school and uni on 3-5 hours a night (but I'm also the exception when it comes to sleep duration, I can't even stay asleep for longer than that usually, if you can sleep longer good for you).
Alcohol or smoking are things I've never even tried, but not for lifting or health related reasons... Just stuff I don't do. You can drink some and make progress anyway from what I've seen.
Try to live close to a gym if possible, or get a basic home-gym setup. A power rack/cage, an adjustable bench, an oly bar and weight plates... Maybe a low or adjustable cable station (many power cages can have one attached) at least if you want to do some bodybuilding.
Not necessary if you get DB's instead, though it helps to have one. Adjustable DB's perhaps (may not need them if you have a cable station available). One of the big EZ bars (not the small curl bars) can be a blessing if you don't get DB's.
I think that's pretty much all.
There are many tweaks that can help with this stuff. People who want it will think of a way to make it happen.
Consider that if you wish to remain drug-free later on in life, but also be very strong, then now is the time where you need to build up your tendons and muscle-mass... Your hormone levels will change for the worse as you get older.
Your current numbers aren't bad or anything, but nowhere near big enough for you to have anything to fall back on if you pretty much quit lifting now and then only start getting serious in your 30's. Your protential will be completely screwed then without chemical assistance. HRT may be legal now, but there's no telling what the future will bring. And mere HRT dosages may not allow you to reach your goals later without muscle-memory and stronger tendons from earlier in life.
It all depends on what you want and what motivates you to train... But usually, unless just looking generally fit is your end goal, then your 20's are your golden years for strength training. Getting serious in your mid thirties will mean that all you can achieve is pretty much "looking fit" and lifting some moderate weights (barring drug use).
If you are motivated by poundage progression and/or you want to get big, then a long lay-off is going to make achieving your goals impossible barring drug use.
On the other hand, if we're just talking 2-3 years of intense schooling with no heavy lifting and you're in your teens or early twenties, then don't worry too much about it and just do what you can to get your life set up the way you want it to. At least if you will really have no access to weights.
So to recap... Be flexible. Think of ways to become more flexible. Optimize processes in your daily life.
Not that hard to do if you get into the right mind-set, really. Frees up a lot of time.
From your OP it sounds like this mostly what you need to do, really. And learn not to obsess over one thing to the exclusion of all else.
Good luck, brother.
Can't offer any specific advice on the gunsmith -thing. If the marines won't allow you to do what you want, how about trying to get in contact with an arms manufacturer? Possibly becoming an employee?
Or at least doing some social networking and getting to know some employees who can maybe help you further your knowledge (and possibly help you get a job there eventually, if you wish).
Or maybe working at a range or something, I dunno... Not sure how these things are handled in the U.S.