Car accident(not at fault)

Hi all! Location: Mississippi

Okay so I think i added the right flair. But alas. Essentially may 20, car accident occurs. At a stop light, stopped, about maybe 1 full car length away from car in front. All of a sudden dump truck to the assend and shoved into the car in front.. hired a lawyer immediately because I know from looking at the pictures, car is totaled. No airbags deployed. Extensive medical damage to back, herniated disc, possibly surgery, lost work… a lot of work due to pain and not being able to really move most days. Also a lot of mental health issues arose from said car accident. Facing eviction, due to having to pay up the rental car, because the car they was totaled was from a BH,PH, obviously no credit to purchase a new car, in fact even car rental places turned me down due to credit, didnt know that was a thing. Anyways, insurance payed what they could. However the lawyer hired said the quickest way to get anything was to go after UM. Because I am in financial strain NOW. He said it would be within that day, originally. Then changed to ot would be a lot quicker. For context, the dump truck that hit, did not have any insurance, or their insurance is claiming not liable due to mechanical error. Dump truck is not registered with DOT or a business.. its personal use dump truck. Originally agreed to the 25k um because was told it was quick.. now im learning it could still take weeks, months.. im facing eviction basically today if I cant pay rent and he knew this last week. Everything was perfect before the wreck. I hadn’t been late on rent, all of my bills were paid and I was in the process of saving for a newer car.. I barely had 1k saved up before the accident. Which had to go to rental car last month.. just alone in rental car since June 19th have paid over 3k.. but I dont have that consistently, im paying by the week because its all I can afford and it is digging me in a hole I cant get out of… is UM the best way to go about this if im already losing everything anyways??? For further context i have not signed any legal documents stating I would accept the 25k YET. I have only verbally agreed with lawyer to pursue this route instead. But I want to back out..