Here's an easy way to improve the way your mold handle fits the block. With the block tightly closed, pour lead between the handle and the block. This makes the block close much smoother. The lead filler won't last forever, but that's OK, just pour replacement fillers as required.
I've heard of using hi-temp silicone to do the same thing, but I've never tried it.
Does your handle hinge bolt keep working loose ? Install a setscrew.