Can a foreigner open a food stall in Bangkok on a marriage visa?

As long as you're only planning on being an owner/investor, the only restriction you need to worry about is the ownership requirement of 51% Thai, 49% foreigner.

Therefore #2 and #3 don't apply to you if you aren't planning on working, since those are only requirements for working. And generally you wouldn't be eligible to work in this business even if you met the requirements for #2 and #3 due to the nature of the business.