Welcome to Purrs sorry about your boy
I have had two hit by cars one ended up loosing his tail and he had a 1 inch perfect tabby stump, he spent 4 weeks on cage rest but kept trashing the crate so we sought vets advice and let him out his biggest problem was he was feral but he jumped with the best and never affected his hunting abilities fortunately by the time he became diabetic he was a nicely reformed forer feral called Tiger or rumpy Stumpy
My second Puma was hit by a car and had the full metal fixator treatment and spent 10 weeks in a kitten pen lined with perspex to stop the fixator being caught on the bars
I would get a dog crate so when you are out he can be confined because they will try to jump and no doubt he is on Metacam for pain relief so they think they are fine - in a large dog crate you can get a bed, grit box and food and suggest a clip on water bowl as they do tend to be a bit clumsy
I used catnip and Valarian toys and things with bells on - we have a small kitten post with bells and balls and it kept them interested and active, he will also sleep a lot once the vets pain meds decrease and you are in charge of the metacam, my advice also cover the flap completely he will keep trying to get out because he can see it - I used carboard taped over the one that is on our dog run ( came with the house) to stop my Border Collies sticking their heads out of it!!
Good luck and we need a photo feel free to pm me if you need to talk further