Gypsum is also mineral-based. It's just not alkaline. What kind of plaster do you have there anyway? Is it lime plaster? I think you're putting too much energy into it. Don’t drive yourself crazy. If you just smooth out the flaws and unevenness, then paint with diffusion-open painter's fleece and dispersion silicate paint, and afterwards always ventilate properly, you’ll have a 99% chance of no problems.