I will hold my tongue on that except to say how many pages are credited to your solenoid search under the battery tray!This isn't the longest, but it is a long one for what should be relatively simple, "how to tell if my starter is bad or not".
Starters are very simple motors that, typically, either work or don't. But, there are also typically a lot of other stuff, like solenoids, relays, safeties, and wiring that also come into play with, does it work or doesn't it. If you know what you are doing, you can skip a lot of the troubleshooting steps and have success. Even if you don't, you can just replace parts until it finally starts working or you give up in frustration. The other choice is proper troubleshooting to identify the actual source of the problem. Sometimes, there is more than one problem. When that is the case, proper troubleshooting is the difference between a one page thread and an eight page one. Looks like we are almost halfway to the latter.
I never said I took the starter off. " I was very clear" on that. Installed was often sited..
Starter just arrived will get photos now