Welcome! Good luck on Primal!
Wow! What a struggle. It is possible though. Remember, you don't have to do it perfectly. Do the best you can.
You gotta cut out the sugar. Very hard to do, I know. But you must do it.
You don't have to eat 3+ meals per day. Many people here, including Mark, fast until mid-day or even eat only one meal per day.
Lots of threads here about eating Primal on a budget.
It would be great if you could get to the gym but you don't have to. Google body weight exercises.
I spend a lot of time at the computer too. Very essential to get up at least once per hour and move around some. Maybe some body weight exercises or stretching.