There's a difference between gathering intel and snooping. You need to know the facts, but you don't need to torture yourself. I don't agree that what you're doing now is snooping. Your H is obviously lying so you can't trust him as a source of info.
Once you know what the status is, you shouldn't torture yourself by following her on FB or driving by repeatedly to see if they are together. That's snooping and only hurts you more.
M 16 yrs, WH62, P54 3 adult blended kids EA 11/13, BD1 6/14 PA fall 14, BD2 2/15 Piecing 2015, BD3 12/15 Separated 4/16 WH moved OW in 5/16 Divorced 6/15/17