We've did a lot of resurfacing of old plaster in the 100yr old house we used to have. Our paint store guy insisted we use an oil primer on all new plaster finishes because he said a water based primer would allow moisture from the top coats to penetrate down into the plaster and the paint would peel up. We always used the oil primer and never had any problems with any finish we put over it. I even stuccoed walls in one of the bathrooms, putting oil primer under and oil over without any moisture problems in an bath without a fan. So, I vote for one more try with an oil primer and latex on top. You have more patience than me. I'd be going for beadboard panelling by now.