“And if his own posek holds cholov stam is not kosher (as various big poskim maintain), he can’t suggest, facilitate, direct or feed another Jew cholov stam (even one who holds of the very valid shitta that it is not non-kosher).”
Is this your psak or is this the psak of the shulchan aruch, or other recognized posek?
“It is highly doubtful, and certainly not a given, that DD will do much even if it were reported to them.”
You really like to make assumptions that suit your needs, dont you. Have you ever dealt with DD?
“let alone one open on Shabbos.”
Exactly what issur is involved with a non jewish store being open on shabbos? How does it affect the kashrus of the store if you rely on the Rav Hamachshir that he is doing his job properly?