Lots to think about regarding this...
Sorry for not re-reading entire thread - has the doohickey been done? Sometimes, when the stock spring or doohickey breaks, the broken parts will migrate and get caught in the cam chain or counterbalancer chain path. My understanding is this will usually result in catastrophic failure much like you seem to have experienced, but...
- that cam cap bolt that's backed out is not good at all. If that cap is loose, the cam may have moved around and ruined the plain bearing surfaces (which ruins the head). Is the rear bolt on that cap tight? You'll need to remove the exhaust cam and inspect the bearing surfaces for damage.
- even if the cam chain, counterbalancer chains are OK, the exhaust cam and cam bearing surfaces undamaged, the broken KACR may have damaged that exhaust valve (bent valve). Something is locking your engine up. You'll have to dissasemble further to figure it out. Suspect you won't like what you'll find.
- Suggest removing both cams, suspend the cam chain (keep it tight by tying it up) and see if you can turn the bottom end over.
Hopefully others chime in too.