I made test calls to my MyFaves numbers and checked my current usage online; the calls show up coded as MyFaves calls (hooray!).
Vis-a-vis the T-mo data settings, I think those are fine *if* the primary & secondary DNS settings -- and IP -- are all supposed to be 0.0.0.0.
If I understood you correctly, the T-mo Dash factory ROM image has been replaced by the HTC image on start-up. In fact, as long as I can access/edit MyFave settings via the T-mo website, I'm not as worried about access via the phone.
On another topic, I did drop the phone last week and though it was not a far drop, it ended up damaging the LCD: 2/3 of the screen real estate completely washed out. I ordered a replacement, watched a video on how to disassemble the unit and replace the screen, which I did successfully. However, I notice now that the right 1/3rd of the screen has a slightly darker tint. There seems also to be a faint white line the runs from bottom right to top left. None of that interferes with being able to read information on the unit; just not "factory fresh." Any thoughts as to what might be causing that? Something I did or didn't do in the screen replacement process?