I’d not suggest to be friends and if he attempts to take you up on friendship, don’t accept and stir away. He’s not after friendship and it will get twisted to make you look bad. I am very social and would talk to a lamp post and am out decent amount of time without my husband due to his work schedule. Nobody ever messaged me on social media saying how much they liked meeting me. The guy sounds like unsavory element. Don’t ever talk to him again. If his girlfriend starts questioning, he’d say you asked him to connect on Facebook. You’ll have bad reputation. Stay away from all these questionable people.