It's not the sitting forward that will kill you it's the bending down and pulling the seat out at a funny angle.
We had a BMW 3 series and getting the capsule or a baby out of that was murder on my back. Even DH found it hard after a while and he's a very strong person. It's not just that you have to lift from down low but you also have to twist into odd angles to get them out without banging them or the capsule.
You can't imagine how happy I was to get rid of that car and get something more suitable. I got a honda civic and in my eyes it was the best car ever because it had 4 doors pmsl.
You'll be doing yourself a favour if you buy a 4 door before the baby arrives but if you don't never mind, your DH will probably be begging for something more practical within the year - especially since they only get bigger and harder to move lol.

ETA - I still love my little honda. DH keeps trying to upgrade me to turbo this and and 6 cylinder that and I just pretend I haven't heard him (although I am kind of tempted by a 4wd so I don't have to fit stupid chains in the snow).