I would take care of the worn out components ( replaced what’s broken or bad first )
Then move on to the chain issue, you may have a bad engine sprocket and a bad rear sprocket as well.
Take a close look at your engine sprocket, and look for possible sharp edges, uneven teeth, etc ( a bad engine sprocket can ruin a new chain and rear sprocket at no time )
You may have to replace engine sprocket/driver, rear sprocket and chain altogether
Depending on the engine and clutch set up you’re running, some like it at 1/2 inch of play, some at 1 inch of play, etc. Too loose or too tight of a chain will kill the whole thing, including your engine driver.
Make sure you check your chain tension, lube your chain and driver inner bushing in every practice session.