Martin, great piece, very creative.
For new techniques I usually do a few sample pieces to test out different methods.
How I would proceed with your desired product
Sand to 220 grit
Two coats of dewaxed shellac over the entire project, sanding with 320 in between coats
Polyurethane or epoxy gloss coat on all areas except for the resin fill area
Resin fill center last.
Wait 30 days for contact with any food.
If you have a shallow v-groove at the point of intersection of finishes, it will help them blend in better, it will be a barrier to keep your finish from the rest of the plate away from the resin fill area, and likewise help contain the resin when you fill the center.
Looking forward to the finished piece.