Need some opinions on where to go from here...

Yea, I clearance mine to what I thought was enough but clearly it could have gone more. The valvetrain always seemed to move okay with the engine on the stand, but I guess it can't hurt to pull the rockers and check the pushrods.

Not sure if I should just pull the heads and start there with inspecting pushrods, cam lobes, lifters, and head gaskets along with the valves...or if my plan of attack should be something else to check before starting to disassemble it. My compression numbers, plug readings, and leakdown results all point to different things
Have you pulled the valve covers and looked things over? Did you replace the plug wires, you mentioned some melting issues.