Seems to me that “to bear arms in a coat” would mean “to have a coat of arms.”
I have HEARD that “regulated” meant “equipped,” and thus, the keeping and bearing of arms by the members of the militia (adult men) would result in their being well-equipped at those times when they formed themselves into a militia.
I also think that the first clause is irrelevant. The amendment says “The right of the people to keep and bear arms shall not be infringed.”
That is the imperative in the amendment. It is permanent. It is what the people legislated through their representatives. It was put there so that the people could resist the FEDERAL GOVERNMENT to protect the freedom of their states. That is a permanent need and right of the people.
My understanding of the meaning of regulated in use at the time was practiced, drilled or trained. As in a Well trained militia.
You are right (see my above)