Okay, sorry it's taken me a bit to get to where I could get out to work on my car. I hooked strait up to the battery, bypassing the car, and the starter is doing the same exact same thing. When I engage the solenoid the voltage drops to 4.50V. I've got brand new OEM battery cables, went and bought some good little wire brushes, and found this plumbers tool in my shop that's perfect for cleaning inside the battery terminal ends, and it cleaned out the terminal ends till they were nice and shiny copper. I went and had both starters I have tested, for the third time, and I watched both of them spin good, again. I charged the new battery back up to 12.97V, as it was down at 12.22 when I got done experimenting the other day, but with all of that the result is the same; solenoid sticks and voltage drops from basically 13V down to 4.5V when I engage the solenoid.
The only thing I haven't replaced are the terminal ends that connect from the battery to the cable. Lol I guess I can go to Subaru or Toyota and order some.