I totally get introversion, but one bit of advice: you should still try to reach out at least a little bit to your peers in college both in and out of the classroom - the cool thing about going to tech school for college is that you're at least to some degree among your kind! (I really hope the Fall Break LAN Party is still an annual tradition, for instance...nothing quite like setting up a perfect engineer nest in TF2 and hearing the wails of agony from across the room.) You definitely don't have to attend every party or anything, but college is a rare chance to spend a lot of time with like-minded peers in a relatively safe space, so take advantage of it.
The thing about job placement is that it's a two way street - the resources have to exist and you have to be willing and able to take advantage of them. Career fairs and counselors are useless if you don't actually go to them. FIT's are pretty good; they weren't a perfect fit for me, but I kinda entered it all on hard mode (during the recession, non-engineer STEM, thought I'd do academia and changed my mind years later...), and they were still helpful.
One note: occasionally the career management office brings in outside speakers, sometimes people who work in specific areas, other times professional job coaches/mentors. If he shows up, please see Richard Gluck, and participate in his workshop. He was there last spring, as I was working on my move back to NYC, and has been a fantastic mentor to me over the past few months. He talks some hard truths about the modern job search, but they're truths I think everyone needs to hear, and I'm so incredibly grateful to him.
Good job. Next step should be to maintain this state for the rest of your life.
To estimate your body fat percentage, you can try one of these calipers for $14: https://www.amazon.com/gp/product/B00B2MIDFY
If I had to guess, I'd say you're below 15%
For a reasonable estimate of body fat %, calipers like these are pretty inexpensive:
https://www.amazon.com/gp/product/B00B2MIDFY
The easiest way to improve is to cut out useless junk food:
If you're not constantly surrounded by these things, you don't miss them after a short period of adjustment.
Absolutely. Convict Conditioning by Paul Wade is a solid bet, it will help you progress through the basic exercises, building some muscle while your at it. It can be a little cheesy at times but it ultimately contains good information.
https://www.amazon.com/Convict-Conditioning-Weakness-Using-Survival-Strength-ebook/dp/B004XIZN5M
Just checked my phone, didn't have any pics :/ Here's a quick mockup though: http://p3d.in/u8CSu
He made it out of treated 4x4s and a metal rod. It goes right under the bed, so the hamok kinda hangs over it. Freestanding and seemed to work fine for him. The problem was getting powertools. Thats, erm, classified, as those are NOT allowed. :p There's a workshop, though.
If you're really serious about bulking up I would suggest some kind creatine or protein powder. That will really give you a boost. As far as exercises you can do different routines of push-ups in your room. Your school probably has some sort of gym that students can access for free. There you could lift weights or sign up for different exercise programs they offer. Good luck.