Hi Op
I do think that if you talking about your daughter, responses a few of them would be different,
It's called being sexist ,equality work ways male /female
I think your gut feeling is spot on ,as he seems very uncomfortable going quiet ect with his girlfriends bantz,
Also your daughter has noticed too,
It could be a girlfriend is immature for her age too,
But that is not a good enough excuse,
I do feel that sometimes his girlfriend could go Dutch with paying for stuff, instead of your son paying for everything,
What you need to do Op, is encourage to have outside interests hobbies and still meet up with his good mates aspect of life too,
It's natural at such a young age his first love that his feelings/relantship will seem intense ,
Also I sense he has low confidence issues, why is that? Could be just his age, or something else ?
Look into that,see if he needs extra support with that too,
Encouraging him to have outside hobbies interest will help to gain confidence too