The signature chain looks okay to me (and the hash sum is the same one that I got when I downloaded it) but I don’t use the portable version so I can’t answer your other questions, sorry.
The SHA-512 is:
Checking the hash sum and the Microsoft Digicode is best practice to be absolutely certain that the software is authentic. The former (the cryptographic has) is more reliable than the latter (Digicode) but it’s less user friendly.
The file is listed okay on the famous virustotal website.