The longer you stay on the T-lowering protocol the more dramatic of an effect it will have. 48 solid hours of zero food, alcohol, caffeine, twice per day training, and zero sleep will bottom out your T levels, especially given the 400-range you're currently in. For "normal" people I would say a week of these activities.
I would suggest telling your primary doc that your sex drive has sucked, and that you don't get fully hard a lot of the time, even while masturbating. You have mild depression most of the time, poor concentration, etc. Ask to see an endocrinologist about possible T levels or thyroid. Regardless of if the primary doc retests you first (which will likely happen) or sends you to an endo for testing, do the protocol before any appointments you plan to be tested at so that your T levels suck.
HRT will decrease sperm mobility and number, making it harder conceive, but it can happen. My doc was concerned with this being an issue for me, but I have had a vasectomy so it didn't matter. Tell him that if you plan on having kids that you'll try some stuff to increase sperm mobility, you may stop the HRT for a time to see if that works (last resort), or if everything fails that you'll just not have kids.
Say that you'd rather have a lifetime full of feeling "normal" than sacrificing that just to have kids. You should come first, kids second. It also might not hurt to say that you didn't plan on having kids anyway.
As far as homebrewing, it's very easy to create a sterile end-product. Nothing is sterile until the final filtering anyway. It's not rocket science. It's also a lot cheaper than the pharmacy charges, which was the reason I began homebrewing. I started to do cycles of stuff since I already figured I was f-ed up, but that's another story.
It sounds like you've got plenty of support here as far as how to go about doing stuff. I would also say that at your age, with those levels, and if you honestly thing you are lacking something in your life, that HRT may be beneficial. You can always decide to stop after a couple months with no damage if you feel it's not what you thought it was.
One last thing, the endo will prescribe gels at first. Take them and go with it for a month until you check back in with him. Tell him that the gels are a pain in the ass and that they smell, and that since you sweat a lot and are active that they never fully dry and stay sort of slick.
You also have to use the gels as the doc will test your levels to determine dosing. Don't ask for injections right off as most endos will be a bit weary, especially at your age. You just have to play your cards right. Finally say that you want to try the injections as you know someone (friend's dad or whatever) who does injections and said that he thought it was much more convenient and less hassle.
They'll likely prescribe something like every other week injections of test E or C. If you can, ask if you can self-administer at home so you don't have to run back to the doc office all the time and pay the copay to see the doc, and it'll be more convenient for traveling or whatever. A nurse will show you how to do it and you're good to go.
I would then suggest doing every week injections, and also ordering some 25g needles on your own, as they'll prescribe something like 20g, which is just ridiculous.
Take the above info and do what you need to get injections. I would suggest not getting the gels for the above reasons. Make up reasons not to try the patch or buccal tabs, unless that's something you wish to try. Either way you won't get enough T for a cycle, but you're dong it for medical purposes anyway.
The patch and buccal tabs work well, but the shots will honestly give you the most bang for you buck. I would shoot for getting 100mg/wk prescribed, or 200mg EOW. I first started at 200mg/month... let me tell you that I felt like shit for a while. It'll be a roller coaster until you get everything worked out.