You sounded pretty unhappy in your first post, like you're having trouble holding it all together. But you've already gotten some sensible advice from your boss and this forum.
1. College is important. Grades are important. Jobs just come and go.
So, take out loans and try to cut back your work hours and maximize your grades.
That, not some temp job, will determine your future.
2. It's ok to take a summer off and graduate later.
Why are you stressing yourself with an absolute graduation timetable?
You're WORKING full time in college; you're allowed to take an extra semester or two to finish.
3. Learn to say "NO" to the job demands.
It's hard, but this isn't a real job--they've made no permanent commitment to you. So, it's ok for you to cut back your responsibilities and explain, "Sorry, I'm going to college full time." If you don't learn to say "NO" now, you'll get exploited all your working life.
--Hey, you don't have 5 hungry children to feed. So enjoy life a little. Take more time, borrow more money and cut back your duties at this temp job, (where frankly, you're getting used--that's why the people are so nice!).
Me--I was tight for money and in a big hurry like you, so I blasted through college in only 3 years. BIG mistake. Be happy, instead. And keep your grades up! (OK, maybe those two goals are somewhat contradictory.)