No, I don't do cardio only when dieting. I base my cardio on what I see with my own body. If I start feeling sluggish or if I feel I need to control my body weight, I add in more cardio. Some of you need to get out of the concept of simply "using a program". I don't write out what I will do like that. I did cardio Saturday and Sunday. I didn't do any yesterday.
As far as what is most effective, again this is individual. I have dieted down before doing high intensity cardio for longer period of time (as in 45min). I lost muscle mass and body fat, both in almost a 1:1 ratio. I have tried long duration low intensity cardio (like walking on an incline) and I kept my muscle mass. Now, I tend to focus on my food intake more than anything and use low intensity cardio. I worked too hard for the muscle I have to diet it away on a treadmill. I tried HIIT before but not long enough to be able to notice that much of a difference between that and Low intensity long duration cardio.
Yes, you can gain strength without bulking. That has never been an issue disputed. You can also gain muscle without bulking. Will you gain as much strength and as much muscle as someone who goes ahead and puts the extra weight on with intentions of dieting further down the road? Not in my opinion. You also won't gain as fast. In that aspect, I can only go by my own experiences and I know very few people who have increased their lean body mass in excess of 80-90lbs without ever bulking up. Your goals determine what you do. You have guys on this forum with 12" arms who think 15" arms are big. I started training with 15" arms and compared to the guys around me growing up, that was pretty small. There must be far more weaklings walking around lately.
Also, why do some of you keep mentioning Cressey? If my goal was to weigh 165lbs, perhaps he would be someone to keep pointing out. That is not my goal and he COMPETES in a certain weight class. How many other guys do you see walking around at 165lbs lifting anywhere near that? One exception to a rule does not mean you follow the exception. Isn't he a power lifter? Why then do people bring him up to "bodybuilders"?
I have no idea what your stats are. To some skinny kid weighing 130lbs, it is more than easy to misunderstand what is fat and what is simply their body changing as they grow. Your face filling out doesn't mean you gained too much body fat, especially if you were extremely lean to begin with. Without seeing what you are talking about, no one can jump to any conclusions. Other than that, YES genetics are an issue. If you are obese, you shouldn't be "bulking up". If you have a slow metabolism, you eat according to the progress you are making. Don't think so hard about this. You make changes based on what you see, not what someone wrote down for you to follow specifically unless you are such a rank beginner that you don't know anything about how your body responds.
If you are lifting weights, why would you think you would be a "skinny fat guy" at all for very long? What are your stats? If you still qualify as skinny, perhaps you weren't gaining as much as you thought you were.
No, I don't "worry" about things like that. I train to avoid injury. I know how my muscles work and what exercises will put them at risk. I know not to bring the bar down until it touches my neck on behind the neck presses. I know this because I understand how my body works. I stop the weight at about ear level. No one had to teach me this. I picked that up on my own from all of the other reading I have done and simply watching, listening, and talking to others. Training this way has taken me from about 150lbs to where I am at currently at about 265lbs. I understand that everyone won't pick up on things like that. I know that I recover fast. I don't have the issues that some people seem to have. I don't get injured easily. I am just being honest with you. The only issue I have ever had is my knees and that is because of an accident I was in as a kid. I won't go into detail but it screwed up that joint.
If by singles you mean "one rep maxes", I haven't done that since high school. It is useless in terms of strength gains in my opinion. It is simply a test of where you are, not a way to get there. There is no specific number. If I write "3", then everone will think I go as low as 3 reps all of the time. The same if I write "4". It varies. People who have been lifting for a while don't do things that specifically as to ALWAYS do 4 reps or ALWAYS do 3 reps. If I move up in the weight used and I get that shit 2 times, so be it. I will keep going up to that weight on the last set until I can get it up enough times to justify adding even more weight.