As to the Rambam you keep quoting, I have already replied that it doesn’t apply nowadays as we can’t do what the Rambam finishes off his halocho with, i.e. punishing those who don’t in beis din. Don’t you think it noteworthy that the Rambam writes specifically לכוף which means “force” them to keep mitzvos? Is that what the lubavicher rebbe said to do?
If Halacha would say “You’re not allowed to carry on Shabbos, and if you do, you’re Chayav Misah”, would you say that it’s muttar to carry on Shabbos since we don’t have a Sanhedrin? If we have no Achrayus on them, and them keeping the 7 mitzvos is bad, then even if we could do the second half, why should we force them to keep anything?