You might consider Saint-Rémy-de-Provence. It's small, but big enough to have some of the things of interest you mention. In particular the ancient Celtic/Greek/Roman ruins at Glanum on the edge of town, and the asylum where Vincent Van Gogh spent time late in his life are worth seeing.
I've always driven my car there, so I'm not familiar with transit offerings, but I would imagine if you wanted to go to some of the other places in the area (Avignon, Aix-en-Provence, Arles, Marseille, Cassis, etc.) you would have to first take a bus to Avignon, so there probably would be a good time commitment -- for example if you had an interest in taking a piloted boat tour to see the Calanques from Cassis (highly recommended, by the way, if the weather is good), an overnight stay in Cassis before you take a boat in the morning probably would be needed.
It sounds as if you've had good luck with restaurants. I would characterize food in France as uneven. There's good, and there's not so good. In my view, it can get a bit monotonous outside of the diversity of large cities because many French restaurants are stuck in tradition. Some love that, but after a while, one wishes for a bit more variety. At least there are regional variations, from the Charolais beef of Bourgogne, to the Germanic offerings of Alsace, to the cheese and seafood of Bretagne and Normandie, and so on.