You can only get an extension for one year or as long as your passport is valid until whichever is the shorter. The fact that you only had 9 months left when you extended means you only got an extension for 9 months. Completely normal.
You’ll have to get the stamps transferred and apply for a new year extension when that stamp is running out.
When you get your new passport you take it along with your old passport to the office that issued your extension of stay stamp (it’s not a Non B visa) and get the stamp transferred.
No idea why you think it’s a money making thing as the transfer is free.
Using a valid visa there should be no time limit that you need to stay out of Thailand for.
There may be some land borders that insist when using visa exempt but shouldn’t be an issue with a valid visa and almost certainly at no airport entry.
The reason itself doesn’t matter, but if it’s for “long term stay in Thailand” Wise try to route it as an international transfer (if using Bangkok Bank) rather than a domestic transfer.