I would strongly recommend hiring a lawyer to help dispose of the new case in a manner that does not violate your felony probation. I recommend hiring a lawyer before court or asking for a continuance to hire a lawyer. I suggest going to court tomorrow after having talked to lawyers today and gotten prices. That way when the judge asks what have you done, you can show that you have taken steps to try to hire a lawyer. Most folks show up and have done nothing.
I would highly recommend hiring a personal injury attorney. The insurance company is required to disclose their policy limits. There are more than likely other insurance policies to pursue including your own Under Insured (UI) policy. Be careful dealing with an insurance adjuster on your own, there are certain time periods to file suit and they can talk you right past them, blocking your ability to collect.
The situation described would indicate that you are guilty of following too closely if you were unable to stop from striking a vehicle in front of you that stopped. The condition of the pavement would be irrelevant for purposes of determining criminal liability.
There is no set time limit. The accused has a right to a bond after 90 days if they are not indicted. Once a bond is set the time period goes away. I would encourage you to hire a lawyer who can try to put pressure on the State to indict or lower the bond.
If you have a had a year to take a 20 hour class it is not likely you will get an extension. The class is risk reduction dui school, not defensive driving. It is a requirement to get your license reinstated. For a first DUI you could have completed the class within 120 days and already had your license reinstated. I highly recommend you take a day off of work or got the class on the weekend or evening. Different places offer different classes. It doesn't matter where you go.
If you are on probation, the only person who can take you off probation early is the judge. You would need an order from the court stating your probation has terminated. The probation officer has the discretion to make your probation "non-reporting" meaning you don't have to show up every month and pay the supervision fee. I would recommend filing a motion to terminate probation once you have served five years on probation and had no violations.
There is a minimum period of incarceration of 15 days for a 3rd DUI in 10 years. He will also be declared a habitual violator and lose his license for 5 years. DUI Courts generally have lesser jail time components because they are more treatment oriented. He could get up to 12 months in jail. My guess would be 90-120 days, but it depends on who the judge is.