You may not be able to convince everyone around you that you're doing the right thing, but you don't have to subject yourself to endless second-guessing from others, either.
As long as you don't think he's just pretending not to mind for your sake, it sounds like he has truly accepted that blow jobs are too difficult and painful for you to perform, and he's still very satisfied with your sex life. Take him at his word.
It's one thing to be a high achiever; it's quite another to privately sneer at your girlfriend's friends after feigning friendliness because they have the "misfortune" to drive a bus for a living.
There's simply no way you can tell a woman you work with that you disapprove of her relationship with her adult child, no matter how much you think it would be better for him to move out.