Sorry for the delays, it took me a while as I scored nice deals in the 2nd hand market over here; secured a Xeon, mobo, 24GB DDR3 RAM and an Intel i340-t2 NIC; this meant that I needed time to set up my new OMV rig.
When I was using the new OMV rig, similar speeds are still noticed. Then, my Windows Explorer started to act more bizarrely, even crashing the entire computer during normal operation regardless within itself or with the OMV rig. I decided to bite the bullet and went with an In-Place Upgrade of Windows 7 Ultimate (which is what I am using) as I suspected Windows as a whole is corrupted.
This wiped out all my Windows updates and I had to deauthorise iTunes as per the warning given by the Windows installer, but other files and programs are unaffected. Getting the computer back to normal after that took me another 3 days (we are talking about 300+ updates and having to reinstall some of them multiple times).
Thankfully, this resolved practically all issues with Windows Explorer! Currently, I can hit up to 100 MB/s without any SMB tweaks mentioned above, and 120 MB/s with all SMB tweaks mentioned above.