If they find that you are not still in the country they can, and do, reject your application. Lots of the time when they have doubts if you are still in the country they will ask for a copy of every page of your passport, even the blank pages. You can take your chance, and risk the bt10,000 application fee if you are wrong.
The only bank that has been affected, because of all the scam/money laundering accounts tied to a Pattaya branch, is Bangkok Bank. Kasikorn is not affected concerning existing accounts. The only thing going on with all banks now is they won't open New accounts for those with tourist entries. I haven't heard of any other banks closing accounts. By all means though, keep all your details, including your visa, updated with your bank.
Anonymous participant a type O visa extension based on Thai wife is much better than the DTV. It is cheaper by bt100,000 too. And, you can work inside Thailand, getting a work permit, with it. It sounds more like you don't think the marriage will last.
Download the DLT Smart Queue app, and register. This will also give you the link to watch the one hour video, with timely questions to make sure you are watching, giving you a qr code to show at DLT at the beginning of the application process. It saves a minimum of an hour. Having the queue number saves lots of time. In Bangkok the main DLT offices across from chatuchak market is dept #5. I made the mistake of thinking it was 1, being it's the main office...lolol. By doing these, and having all the documents, you can be in, and out of there in less than an hour, and a half. I'm not sure if they've started having everyone getting a new Thai license take the written test yet, or not.
He will need a sponsorship letter from you, and you should have the equivalent of bt1million to be on the safe side, as changes are made weekly as abuses are tallied. What was allowed last week isn't automatically what is allowed this week.