I just downloaded Fixit it is not corrupt.
It is the malware doing to Fixit what it is doing to the other programs that will not download or run.
Some have had success by downloading from Safe Mode with Networking. If it will d/l and extract then run from there then run once more from normal mode.
I will do much cleaning in Safemode but...
To be able to find the programs and services it needs to stop and kill it must be run finally in normal mode
Mike