Welcome to the post-college real world :)
Honestly, there isn't enough info in your post for anyone here to give a proper answer. eg the city you are in makes a difference. No worries, some general things to think about in your last year of college:
1. Don't work for a bad boss if you can avoid it.
2. Figure out what a bad boss means to you. But my criteria (especially right out of school) includes working for a boss I can learn from and a boss with high EQ (a boss who understands when his/her employees are stressed or exhausted or confused it makes a big difference).
3. Learning how to not burn a bridge is smart. But burning them happens sometimes. Try to please everyone and you will lose. It gets easier with experience (plus if someone is talented at their job, these ppl seem to be able to not burn bridges no matter how big an asshole they are). Maybe one reply to your boss could be: 'Thank you. Please let me know when you get that contract so I can discontinue my current talks with other companies'.
4. Believe in your startup and its product. Maybe more important than a good boss, ymmv.
5. Always be networking and getting to know people in your industry/in your city. Even if you don't call it "applying" I would be reaching out to other startups now. Email them say you are graduating and ask to learn more about what they do.