I was more making the point that it must be the agents assistance that's making this possible and I'm not referring to the funds in the bank.
The OP also states, as you pointed out...,.
"So, if I were to apply for a retirement conversion from this Non-O during the 90 days after the visa itself has expired, would that be an obstacle to getting the retirement extension?''
He uses "conversion" incorrectly.
I'm happy to be corrected but my understanding is that his first extension needs to be based on marriage