The heater looks almost identical to the Webasto that I had. The Webasto had a loud click from the fuel pump and the circulation fan would never fully stop when the unit was on. Have you noticed either of those things with the Russian heater?
I got the D2 . Takes a while to get the van warm but maintains the heat no problem. I wouldn't be afraid of getting the next size up .
Could you rewire with a 12v digital thermostat/controller? $15-20 on Amazon.