Also whats the the point in setting difficulty from VARDIFF to your own ?
That sentence makes no sense to me. But variable difficulty has no bearing on solo mining.
Pools set a higher difficulty for accepting shares to reduce bandwidth. If a pool set your miner difficultly to 1000 then that means approximately one share out of a thousand will exceed the 1k diff and the pool will pay that share as if it were 1000 diff 1 shares.