I mostly agree with your points here, but I want to touch on a few.

He was a failed bush league MMA fighter

He wasn't bad for a regional fighter at all; gave Reis some trouble in his last fight.

and got sparked out by Conor the first day he walked into SBG. How can you coach a guy when from day 1 the power dynamic had been established that you are inferior to him?

I believe the full story as told by most who were there is that he walked in, they agreed to some light sparring to gauge where Conor was at, but Conor took advantage, came out super aggressively and threw a left hook to Owen's liver at full power.

No way did Conor have better striking than an actual fighter on his first visit. It's impossible.

What has Conor learnt from Owen that he didn't already know from Crumlin boxing club?

Everything you see him doing effectively now. Conor himself said that he only occasionally showed up to the gym when he was younger and that he only picked up the fundamentals. Owen can still be credited with improving his striking since deciding to pursue MMA.