Well holy ****, this got a lot more attention than I expected. Posted it then went on with life not expecting this many responses.
1) Re: oral inflation - he was trying to inflate on the surface, should/could have ditched weights but obviously task loading was an issue. I don't know if he tried to inflate underwater or not. I would also say that the attempt to manually inflate made the situation worse. Keep the reg in, ditch weights, swim back to shore. Communicate with buddy that there's an issue. There were definitely some better options.
2) Re: overweight - so you guys are trying to say that with a fully deflated BCD he should have been positively buoyant? Or am I missing something here? When I said we descended to reconnect the hose, that was more a consequence of him being negatively buoyant than a conscious decision. Point taken though about the weight dump, that would have been a better next step.
3) "Your friend should have figured out a solution on his own, since he was at the surface on his own" - yeah I'm not going to sit back and watch my dad drown. Am I going to make sure I help safely so it's not two deaths? Yes of course, but to say he should have figured it out on his own kind of defeats the purpose of the buddy system, no?
4) Some of the responses are pretty holier-than-thou, but appreciate the feedback from the rest of you.
I think we will do some pool dives and skills practice before going open water again.