Inbreeding is somewhat normal in the BP world, especially when trying to prove out a recessive gene.
As for your question you don't know if your 66% het is even a het. All you know is that there is a 66% chance that snake carries the albino gene, and 44% it doesn't. As long as you don't mind getting a bunch of babies that you pretty much have to call normal (not het albino) then you could go for it. I you want to prove the snake a 100% het albino, then you will need to breed it to an albino or a 100% het albino and get albinos. There's no reason you have to breed it back to a parent, any albino or het albino will prove the snake a 100% het or a 100% normal.