My insurance called me and said they would try to settle payment with at fault drivers insurance but we would need to take some fault

I hit a truck it went in other lane car hit it, driver of car had broken ankle. Truck driver got 2 citations fault equipment, ( no lights but one barely working) doing 40mph in 70 mph interstate. After accident I connect his insurance, they knew about it and adjuster called me said to go to tow yard get tags and real lease car to them, i did 3 weeks later my insurance calls to do recorded statement and wants to take car out of tow yard and try to settle with his insurance to do 90% there fault go to 70% and if not go to arbitration. 1 is that how insurances deal generally in these cases ? 2 injured person has lawyer and if they sue insurance and they sue for more then my will pay will I have to pay out of pocket, or they would have to sue me directly to pay. 3 car is in my moms name I am on insurance can the other party sue my mom if it is likely, When do i need to hire a lawyer?