Don't let it be a black cloud over your head; we've all worked for people we can't stand, you will continue to experience it throughout your career. It sucks that your previous supervisor was vindictive, but look at it from the airline's perspective: nobody wants to hire someone who is potentially going to be difficult to work with (even if that isn't really you), so they are giving a lot of weight to a report that your previous employer won't welcome you back. Keep us updated with what happens with your now-rescinded offer from the airline. In the meantime, YES, get a copy of your PRIA so you can see what the airlines will receive. If things don't get worked out so you get your offer of employment and class date again at your airline, time to find a plan B.

Get a letter of recommendation from your former Chief's boss. Apply elsewhere, and then use the HR interview as your opportunity to get in front of a negative report that they likely won't pull for a few days. Explain, in a balanced and professional manner (don't be emotional and take responsibility where you should, don't resort to name-calling) that you had a difference of opinion/personality clash with your former supervisor that led you to resign. Highlight the good work you did for your flight school and the scholarship you received. Show them any and all letters of recommendation you have. If the response you receive dictates it, explain what you have learned from the experience regarding working with/for someone you don't agree with. Above all, don't sound like you're making excuses, the weight is on you to convince your prospective employer that you are well-equipped to handle disagreements and frustration in a mature and professional manner ('cause you will encounter a LOT of it in the flight deck, on reserve, and with company policy grievances). Good luck!