When should I add lactose...

Yep !

Not only no cream in a Cream Ale, no “ale” either. If you want to try a readily available, recent GABF gold winning commercial example of Cream Ale - Rainier

I dunno…quite a few are made with ale yeast.  I think probably more than as lagers, although either way is fine.

Yeah, I make mine with 1056 @ 60F. Makes a very good cream ale. Kiwanda uses ale yeast IIRC.