A DUI is not expungable, it is a traffic offense. You can expunge up to two (2) disorderly persons offenses (misdemeanors) off your record. Contact a lawyer to figure out if you are eligible. It's a 5 year waiting period on a disorderly persons offense to get an expungement.
You should definitely shop around for a better price. That's a lot to charge for a PTI eligible case. Flat fees are permissible but they can not be non-refundable. If you fire an attorney after hiring them on a flat fee, they have to bill you hourly for the work they have done on the file and then refund you any balance remaining. I am not an ethics attorney, this is just my understanding of the permissible fee structures.
Probably none. He can be charged with contempt for failure to appear in court but usually the judge will just give him a fine for failure to appear and no jail time. 750 bail is fairly low also so that's a good sign.
It sounds like you and I already spoke on the phone. If you can't afford an attorney, apply for the public defender. Remember though, with two second degree charges you are facing a maximum of ten (10) years in prison on each offense. You definitely need someone who knows what they are doing in your corner at this point.
You need to get a driver's history abstract from the DMV or the local police/municipal court. If there is a divorce pending you might be able to subpoena a copy, you would have to ask a divorce lawyer that question.