Please keep all your questions in one thread - it makes it much easier to follow and you'll get better advice.
You can certainly charge necessities on your joint credit card. After he files for divorce, you may have to account for your expenditures, particularly if they are unusually high, but there's not going to be any issue with buying groceries, gas for the car, etc.
Be prepared, though - if he does file for divorce, he may cancel the credit cards right away, so you need to start figuring out how you're going to support yourself at that point.