whilst your right on emperor "motives"

The Death Star II is pretty close to the planet... I suppose it could move away but then that makes flying through narrow tunnels totally implausible too. Unless it had already moved.

I think ok so the Emperor gives the order to blow up Endor. Best place for that? Vader threatens to go after his sister if he does not turn. Now the emperor is going to blow them up or what cut the line about converting his sister?

You can't really show any scared looks on the faces of Han and Leia... You could treat it as they would not need to know about it. But you would have to have some kind of dialogue that the Rebel Fleet would be aware of that situation.

I think it's still too tricky and a bad idea to try to recycle an idea 100% and would be better to just see the fleet being slowly degraded in numbers to the point of near defeat.

This only my opinion.