A few things to add:
For one, this rifle hand cycles perfectly. It'll strip, feed, extract, eject, everything flawlessly if I'm doing it by hand. The issues only occur when I fire it.
About the extraction issues:
I'm pretty sure that started when I shimmed the extractor to increase its spring tension. No worry, as I can easily reverse that. The casings weren't torn up, and they're easy to remove from the chamber with a fingernail.
Before I shimmed the extractor spring, the ejection seemed stronger and extraction was fine, but the casings wouldn't always eject, such as I describe in malfunction type #3 in my original post. So this is the malfunction I'd like to focus on. I took a slow motion video of this occurring prior to my temporary modifications to the extractor, and it shows the failure to eject.
Somehow, the casing is staying on the extractor, after the action cycles completely. My ejector is .600 wide, which is actually too long according to 5.56 AK specs I've read on this board. It looks to be right where it should in relation to my bolt, and it seems physically impossible for the casing not to smack that ejector. I don't get it.
Here's that video of this particular malfunction.
0:07 - I start shooting
1:14 - Malfunction occurs