Found the problem with my starter. The original starter was definitely dead, but the new starter is fine. The real issue that I had is the fact that the control voltage line is only outputting a measly 6 volts while I should be seeing at least 12 volts. This little trigger is enough to get me around until I stop being lazy and break out the electrical diagram to figure out what the exact issue is.
I’m just glad I don’t have to crawl underneath the car again with this hellish combination of extensions.
In the above image is a 1/2" drive wrench, a 3 inch long 1/2" extension, a 1/2" to 3/8" step-down, a 6 inch long 3/8" extension, a 3 inch long 3/8" extension, a 3/8" universal joint, and a 14 mm deep socket. All to reach the lower starter bolt. Never again.
Next stop: acquiring, cleaning up, and installing a new oil pan on the engine so I stop leaking oil everywhere.