Pardoning people who can testify against you is a supremely stupid idea: They lose the ability to invoke the Fifth Amendment and can be compelled to testify or go to jail. It works when you want to troll your enemies by pardoning wacko Sheriffs. Doesn't work so good when you are the capo!
Also the idea that the Mueller investigation goes away when you fire Mueller is totally nuts: First thing the House would do is to subpoena Mueller and get him to tell them EVERYTHING. Members of the Intelligence Committee are security cleared to investigate anything they want, so Trump can't slap Top Secret on it and hide it from them. Doing that just makes it all public ASAP. If you leave Mueller alone, he might write a final report the AG can sit on for a while. Of course, if that happens the Intelligence committee proceeds anyway.
I think Trump's options are narrowed to Martial Law or flight into exile if he wants to escape justice.