Check out this thread - many comments, but in particular I provided an basic answer to one of your questions at post #17 and a procedure that may be helpful at post #19:
Synscan alignment
I general, a 3-star alignment will provide more benefit for visual use than polar alignment, but polar alignment is (probably) of at least some benefit even then. Polar alignment will be more beneficial if you only do 2-star alignment.
As for the focus problem, I'm not really sure. I don't currently use a Newtonian, but a "trap for young players" that I recall is not using the provided eyepiece adapter.