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

Bewy said
I do not see a problem with the cap.

I couldn't any cracks visible to the eye, but it does appear there is a rotor phasing issue to me.

Oldmanmopar said
Well I found this upon taking a quick look at the cap

Well like I said several times above , I think you have a Bad cap issue. That's the only thing that ties 3 and 4. Find a matching cap and rotor with brass contacts. Make sure it has a vent to disperse condensation. It would be your quickest and cheapest try for process of elimination.

MOPAROFFICIAL said
Looks like bad rotor/cap phasing.
Also make sure the rotor is pushed down all the way.

Even your average good sealing cylinder will lend some leakage to the crankcase when doing a leak down test via ring gaps.
The air is going somewhere, be it head gasket or rings.. both will enter the crank case or neighboring cylinder.. so remove the rocker shaft and pull the plug on the cyl next to it and put your finger over the plug hole to feel for pressure build.

One thing is for sure is if it's not just a valve hung open due to maladjustment.. its gonna a need to come back apart.

The cylinders that are clean are burning the fuel well... while the others are not.
Bad needle and seat can wash out rings and flood cyls making them extremely rich and blackened plugs as well. You checked the lash and say it didn't really change, so bad lobe seems less likely

Going to try a new rotor and cap, but before I fire it up with that, I'm going run a compression test dry and with oil, as well as add water back to the cooling system (drained last year before the winter) and try a leakdown on cylinder 6 again and see if I get bubbles in the rad, which would point to a head gasket issue and something I didn't think of before. I did the leakdown tests with all the plugs removed, but rockers on, and when I struggled to find the issue with cyl 6, I could not feel air coming from neighboring cylinders as I did check for that. Carb was completely rebuilt with all new parts before first fireup, but anything is possible in there as well.

Went to go run the compression test last night but the battery was dead. Put the charger on and it showed 100% charged. It's only 3 years old so maybe it's gone bad, but I noticed the negative cable post was pretty corroded, so hoping that is my only problem to add to the list