for a divider, why not peices of wood that slide snug into place, and can be moved easily, and maybe sets of predrilled holes in 6-12" incraments or so to screw the divider into place without making it perminant. Maybe find some expanded PVC as a divider, its light and not seethrough.

As for coating it, I know there is a milk based product or something, but i dont know. You could just use Melamine, or put formica laminant on the wood then caulk the corners and you have a nice sealed, moisture resistant, decent looking enclosure.

Silicone works good with plexi, ive used it with acrylic (generic plexi), and stuck well almost instantly and is still holding extremly strong in a spot that is freestanding (on a wall with no bottems or sides).

Ben