How do you know what he has told her for a fact. I has she told you these things? Maybe he didn't actually tell her anything but said he did to get a rise out of you?
lets say he did ....what was his motivation ....pity.???... I'd say this is certainly did damage to his self esteem.
As for going to meet parents or family ...who wrote the book on that protocol. You and I read that to mean serous relationship other see it as meeting someone new....like going to a party and only knowing the host.
When you started out did he stop you from doing similar activities....or did he just have to suck it up? If so remind him of them .....if not then just suck it up.
The red flags others mentioned might be looked at two way ....he continually told you his struggle which was a flag in its self. You encouraged this to take the pressure off ....ease the guilt, etc..... now now you see flags.