Oh your poor boy.
One of my childhood cats had a front leg amputated -iirc, he was a 'grown up' cat when it happened -maybe 10 ish? He lived 'til 19. Some things changed - he couldn't run fast anymore and he rarely left the garden. He also had more trouble jumping up and down to the window ledges (where he loved to sit), so we rearranged the furniture to give him steps. Sofas and beds were ok, but then they are less high, and deeper, and a soft landing.
Eating took longer at first, and we had to experiment a bit with dishes and blocks to make sure that they were bag the right height for him and he was a bit wobbly at first. Because of this, we fed him away from other pets.
We also had to pay more attention to brushing and grooming him, as some bits he couldnt reach and i guess his injuries meant he was less flexible. Nothing drastic though -we just brushed him, and occasionally took a damp flannel to him if he felt a bit grimy! And also his claws had to be attended to, as they didn't seem to get worn down.
Is he litter trained? Ours wasn't, and he took to pooing in the garden, as opposed to a bit of wasteland over a fence he used before. Of course this was fine. And he kept his bottom etc clean. All in all, he coped well, and we just made tiny adjustments that then seemed normal, eg the series of steps made of footstools, tables and sofas. He lived a really long, very happy life with our family incl. us as kids, other cats and a jack russell, and I really don't think he suffered, apart from after the initial accident.
Very best wishes.