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

Heads were new, but you put the old rings back into their matched cylinder. Did you run a compression check on the motor before you disassembled? The lower #4 cylinder and oil residue on some of the plugs tells me bad ring seal. I've never used the same rings again when pulling apart a motor. A quick hone job and new rings are too cheap to risk having sealing problems. That's just my opinion.