You could try lowering the bed temp, but it really is dependent on the bed material. I’m guessing the majority of the printing community is using traditional beds like glass with kapton or blue painters tape. The Lulzbot printers with PEI are a little different and probably require some experimentation. The Lulzbot baselines are always a good start, try lowering from there.
If you need a higher temp dissolvable support material try HIPS (use Limonene to dissolve). PVA pairs better with lower print and bed temps.
Report back on optimal bed temps for PC.
EDIT: I just re-read your post… and just comprehended that you’re using PVA on the surface of the PEI to reduce adhesion. I think that’s fine that the PVA boils off, the purpose to provide a slight film reducing adhesion of the PC.