For gaming, I highly recommend a trackball mouse since it requires so little movement, and depending on the model the buttons don’t require a lot of force to be pressed.
A quick google shows me that these work even on an xbox.
I would suggest a fingertip trackball, and one with the largest ball diameter you can find. The larger the ball the more accurate and less movement needed.
^ Something like this would be good for the first little while, he can drive with the trackball and use his feet to click. There are lots of these at different price points.
For comfort, things to ease the itch and miserableness of the casts that will come. It keeps you up at night.
^ These to scratch itches down the cast. He should put nothing else down the cast, and don’t put it so far down that you lose it. The skin under the cast will become very thin and fragile, anything put down it with a sharp edge could scratch and the warm moist environment could breed infection.
Regarding toilet time, if the bidet you got does not have a dryer function he may need to dry his booty when he’s done. Many homes that have bidets everyone has their own little towel they use. He could move a stool or something in the bathroom and put a specified towel over it to sit on to dry himself.
My condolences to your friend, really glad he has a friend to help him.