I’m so sorry op, I have an almost identical story about my cat who got ran over around November last year. The whole thing was incredibly traumatic.
He also had a broken pelvis and had managed to make his way home after being hit. We found him in our back garden the next morning (after worrying all night) I don’t know how he managed to get home in the state he was in but we thank our lucky stars every day that he did. We took him straight to the vets for an emergency appointment and he ended up staying there for a week.
At first they suggested he be referred to a specialist vet practice for surgery on his pelvis. Then we spoke to another vet there who’s cat had had a similar injury and after looking at his x-rays she suggested he may not need surgery and how resilient cats are and how they can bounce back from things surprisingly well. She was very experienced and reassuring and said we could choose to have the surgery, or go down the cage rest only route. She seemed reasonably confident he would be ok without the surgery.
In the end we opted not to go for the surgery. When we were finally able to bring him home, he was on cage rest for six weeks, then room rest for a further 2 weeks, then house ‘rest’ for an unspecified amount of time. We also had a cocktail of medications to give him to keep him comfortable for the first few weeks.
Cage rest was hard at times, but doable. He meowed a lot, but one of his pain meds had a sedative effect which helped, he slept a lot during that time, and I spent a lot of time sitting next to his cage keeping him company.
Up until about a month ago he had this awful limp, couldn’t really jump up onto the sofa or scratch himself with the affected leg. I was worried he was still in pain, but he seemed ok in himself. Then, all of a sudden one day I noticed the limp had gone, he could scratch himself and started jumping up onto things again. It seemed to happen very suddenly and although he’s not 100% the same, you really wouldn’t be able to tell unless you looked closely. I still can’t quite believe it. He hasn’t been allowed outside since, but as the summer months draw nearer it’s getting harder to keep him in and he’s asking to go out a lot.
My cat is also much older than yours, he was 9 at the time it all happened and seems to have recovered well. I really hope yours can too, he definitely has age on his side.