I'd listen to Bill with his depth of knowledge.
DTV: While you can get to increasing depths of knowledge their front line support is at times lacking. Sure they basically want to keep every customer but in the big picture mobile is a smaller portion of their business and their knowledge about mobile is more limited.
I purchased a receiver and dish that I installed. But times have changed. Receivers are leased, no longer shipped and DTV seems to have little interest in DIY.
Bottom line: Keep at it, consider a coax directly from the dish to the receiver - are you positive the coax is OK and/or you're using the right one?