moving this thread to malware removal.
Looks like you've got some work to do, namely find out where itdownload_stub.exe and InstallManager.exe are coming from. They are in temp so my bet is another executable is extracting them. It happens when you run dSS so my bet is that your copy is infected.
dSupportSuite.exe v3.1.7 is 1,871,224 bytes. Your copy is likely a version or two older but the size won't vary much beyond that with the minimal changes I've made to code recently. My suspicion is that either your dSupportSuite.exe is significantly larger than it should be, or your installer is significantly larger than it should be. My generic installer is 4,233,590 bytes but that can vary a bit depending on the size of your logos or anything else bundled in.
Still I'm skeptical of your PC with dSSMC on it, and it's also possible that you have an infected Inno Setup compiler. My Compil32.exe is 1,102,848 bytes and I think that is v5.5.3 which has been out for some time so yours should match that. I don't see a point in hashing the file as most malware just add to the file size when file is infected, only sophisticated viruses would make an attempt to conceal the extra code.