Realistically, what you do in your home online is your own business. Don't go advertising to everyone that you're working and you should be fine. You're far from the only person who would be doing so.
Not for many months. DTV holders are not eligible to open bank accounts as a DTV visa is a tourist class visa, and banks are no longer willing to open accounts for tourists.
the non-O IS the marriage visa. So you saying "this is for the marriage part" makes no sense.
You applied for an extension of stay of your marriage visa, and your extension is based on being married to a Thai.
So you should technically keep the money in your account until you go back on the date of your under consideration stamp to get the full extension. Likely nothing will happen if you touch the money sooner, but leaving it there is the 100% safe way.
you said you applied for the visa. A non-O visa is a 90 day visa. You only ever have this once. Every application after that will be for a 1-year extension. You need to know which one you applied for.
Officially, they can ask you to prove you still have the required funds when you go back to get the full stamp in your passport. It's not likely, but it's possible. The general guidance is to not touch the money until you finish your under consideration period and get the full stamp in your passport.
And if you're talking about the visa and not the extension, you're going to need the money in your account very soon again when you apply for the extension, so it's best not to touch it until after that's all done as well.