Updates:
I drained the oil, there was probably about 6 liters in there. It occurs to me that since the car had sat still for 3 weeks, with only a few instances where I had it idling for <2 minutes, is it normal for the valve area to dry out?
The pinging is fixed!: I decided to repair the busted push rod. (Some used ones are in the mail as well). I installed that just now and the car idles!!! (very slow, but steady). It seems the broken push rod was the source of the pop/pinging. If that's the case, that means I drove/limped about 3 hrs with the broken rod & rich fuel mixture. (Oh the damage I've done). I still can't figure how it broke in the first place, but there was some significant backfiring which maybe dislodge the union which lead to a quickly deteriorating situation.
More issues: I still don't feel comfortable letting it idle for more than a few moments, but I'd like to know if the fuel pump needs help or not. That and I noticed some vapors coming from the hole in the valve cover where the oil line runs up into the rocker assembly. This has me quite worried so that's item #1 to look into. Some people say it's normal, but I worry my head gasket or even the block could have been damaged.
If by some stroke of luck, the engine & oil seem to be doing okay, I may try revving and working on the fuel mixture ahead of the sniper install. Right now it's running quite rich as I can smell some gasoline out the tailpipe. (which makes sense for a sea level carb running at altitude, right?)
I can't imagine getting out of this without needing nearly a full engine rebuild, but for the next year or so I just need the car to drive 2 miles per day, under 40mph. Should this change the calculus of the fixes at all? I certainly wouldn't want to do anything to further compromise the engine, but maybe good enough can cut it for a short while until I have the means to pull the engine.
Anyway, I'll appreciate any and all advice on my situation! I'm quite sure I'm in over my head now, but I'm going to keep plugging away! The more I learn the more that's wrong, but dang if this isn't fun. What a cool & straightforward design these old beauties had.
Thanks again for all the assistance, both in this thread and throughout the forum.