/fa/ - Fashion

Okay I know this belongs on /fit/ but bare with me please.

>5"11, 8 stone (112 pounds).
>TDEE is 2100
>BMR is 1550

To put on weight I need to eat +500 on top of that, which is 2600.

The problem is, I was eating +500 on top of my BMR which equals about 2100 calories, that was fine and I was just about managing it.
I am insanely poor, I cannot afford a gym, and thus I was going to do sit-ups, crunches, pull-ups and chin-ups etc whilst I was gaining weight to stop myself from becoming skinnyfat.

BUT, apparently I need 112g or more(?) of protein to even develop muscle anywhere, and that's something I can't achieve.
Trust me, I have been eating to the max, peanut butter sandwiches, milk, everything I've been trying as hard as I can in terms of diet.

So what do I do? Is eating +500 on top of my BMR not going to cut it, do I absolutely need 2600 calories?
If so I'm doomed to be a skeleton for at least a few more years, you're my last hope /fa/, /fit/ does not take kindly to me.