Looks like he was a doctoral student. Can't find any trace of him today except people alleging he's the source of that definition. And judging by the thesis mentioned, it seems like he was a cognitive scientist or something along those lines - not sure why he's opining on history, law, or the meaning of words in the 18th century. I mean, he's welcome to, but he's not an authority.
Well, all he did was profess that these quotes do indeed exist in the OED. Without access to the same texts there's no way to verify those quotes, so they're all trash now and I'm pretty surprised there's no other trace disputing or confirming the existence of these quotes. Maybe you're the man to do so.
the military should be under strict subordination to, and governed by, the civil power. Maybe the military means only standing armies
There's little doubt in my mind that the "military" is in reference to a nation state's standing army. Why else have the distinction between militia and military to begin with? You're reaching here.
Maybe the military means only standing armies, but I somehow doubt they want bands of armed citizens roving around not answering to the state in any way.
What exactly do you mean by "they"? I think it's pretty clear, if we accept your interpretation as correct, that active armed citizen militias is exactly what this means. Armed citizenry, organized and well practiced with their weapons that can act in defense of the state and -- as seen referenced elsewhere -- to protect themselves. But, I will concede not by all of them or in equal levels of importance.
The founders feared a Federal government going around and disarming the state militias. This is known as the collective rights model.
Note that he refers to the militia performing military exercises, by the way.
And there's references from George Mason, Madison, and Hamilton that mentions these militias should be actively training. Separate of the Federal government's powers with these actions protected by the nation's founding document.
I think it means "the people" broadly and is meant to protect against blanket seizures/prohibitions
We have the 4th amendment, and even so it applies to everyone individually. I agree though, the 2A was made to protect against disarmament.
You're wondering what qualifies as disarmament and what doesn't. I don't think a handgun ban is tenable given the current interpretation of individual ownership. Of course, this depends on where you live. Some circuits will uphold restrictions that others would deem unlawful. California has taken it pretty far with some rather niche restrictions and their policy on concealed carry permits, while not out right banned, are de facto banned in many places due to "may issue" laws.