everything looks good, no need to format,
go ahead and install 4.20.707.6 stock you wanted (since it doesn't automatically wipe, you need to do it yourself as i mentioned previously)
check if the file is OK, MD5 should be: 6A4AEE254ED7AC32EAF9292D72D9E2D3
your internal storage will remain intact, but settings and apps+data will be gone, you either need to use HTC Backup or TiBu (or whatever method you usually use) to restore the things that can be restored, and manually setup the rest.
i had a htc backup done 2 days ago so now i'm restoring through that to see . . .