The shaft is hardened steel, but the lever isn't. The spline is stripped, so the lever just spins around on the shaft. Should I maybe use epoxy to stick it in place? Drill a small hole (very small) and insert a set screw?
you could braze it or weld it there isn't much need to take that thing apart.
If you don't have access to welding equipment you can get a small propane torch and silver solder it and it will work good as new.
one last resort would be to drill all the way through and roll pin it this would be the very last ditch effort as you will weaken it.
how far away are you? If you want, send it to me and I'll either silver solder it or braze it or gas weld that little booger let me know all I ask is for you to pay for the shipping. sound fair?
I've done repairs for others on this forum and so far none have complained I deleted them before they could