I have never used the PB glue. I used Titebond, which is probably similar. It it most likely a PVA (alphatic) glue... Funny that it doesn't say on the website. I would leave the clamp on overnight at least. My Tightbond bottles says not to stress the joint for 24 hours...so I'd leave it clamped that long at least.

I would also fill the gaps with veneer. It's cant' make the joint less strong, and might help a little ;-)