Should I amputate his leg?

Amputation really is the best option a lot of the time unfortunately. I’d need to see the X-rays to tell u if it’s the only option but lemme explain why amputation is such a good option first: when a young kitten like that needs a cast they usually have to be very very sedated while they heal so they don’t re break the bone or cause any other issues. This means that they miss out on important kitten learning time. Casts also aren’t a guarantee that the bone will heal correctly. The bone may be so fractured / shattered that it heals into the wrong shape or in a way that causes pain/discomfort later in life. Whereas amputation is a much shorter healing time and they aren’t usually required to be sedated much longer than until the stitches heal up most of the way (like two-three weeks, sometimes vets do less or more depending on how the kitty handles it). Also, it’s worth noting that cats and dogs don’t usually react to amputations the way that human patients do. They don’t have as many issues learning to walk again and they tend to handle it better emotionally as far as we can tell.