You are obviously very frustrated and I can understand why. Unfortunately, you did not provide any details in the message that would help solve the problem. I assume you have shared details with WG support, but that doesn't help us.
Meanwhile, you think there is no possibility of help from forum members. I don't agree. You should start another thread. Pick one PC where you can't get TMG to work, and in that thread, describe what is happening. Members here will ask some questions and provide some advice. It's best to work with a single person rather than a group because the process has to be organized. Based on the evidence--the information you supply--the helper has to narrow down the possibilities until the solution is found.
I was helping a person install one of my programs last week. She said that when she started the install program, nothing happened and the install program icon disappeared from her desktop. After determining that she had a valid copy of the installer, we discovered that her anti-virus program was the culprit: it was preventing the install from running and removing the install program. Evidently, it thought the installer had a virus--it doesn't--but worse than that, it did not communicate what it was doing. When the anti-virus program was turned off temporarily to run the install, everything went smoothly. I am not suggesting that the same solution will work for you, just giving an example of one of the many things that can interfere with installing and/or using a program.
Given that thousands of people are using TMG v9 on a wide variety of PCs and operating systems, it's very likely that it will work for you. To achieve that, you need the help of someone who understands how to diagnose and solve the problem. There are a few people on the forum with those attributes.
And, by the way, we won't be gone in December. WG Support will not continue, but user-to-user support will continue.