You dont have any numbers bullet points in your question, so i an still not sure what point "#3 above" relates too.
the crux of the issue that you are having is that the install button is not available in the extension manager, therefor, you cannot use the extension manager to install new extensions.
I have given some advice that believe should correct the issue and make the install option available in the extension manager, but if this advice is not working for you, the people to help you get it working are Adobe.
I'm not trying to shift responsibility simply because I'm being lazy and dont want to help. If i had other advice for the problem, I would gladly offer it up.
My suggestion to contact Adobe support is not just to search their forums, but get on the phone and contact them directly.
