Older car and issues with infant seat

Hey ladies,

So I’m currently driving a 2000 Chevy Malibu while I’m waiting for my actual car to get fixed, that’s unfortunately taking longer then I expected. Anyway I’m just days away from my due date and I’m freaking out because the infant seat I purchased isn’t sitting correctly in the Malibu. The back seat comes upward towards the knee area which makes the butt of the seat incline. I hope that makes sense. So when I strap the base in with the seat belt because again it’s a 2000 and it doesn’t have the latch the base of the infant seat is at a heavy incline which I know isn’t ok. The base only has a red line that I’m supposed to level with the ground to ensure proper installation which I find to be extremely difficult to use compared to the ball/bubble indicator that was on my daughters seat. The user manual states to use towels to increase the height of the base to install the base correctly but when I use towels to bump it up a bit the base slides more then an inch front to back and side to side which again isn’t ok.

So now I’m freaking out cause I can go into labor any minute now. Should I run out and buy a new car seat? I’m terrified that the incline will obstruct my newborns airway on the car ride home. Buying a new seat isn’t ideal but if I have to I will. My daughters infant seat 6 years ago had an adjustable block in the front so this issue was avoided.