Incorrect. Most installation commanders are O-6, Captains in the Navy and Colonels in all other branches.
Yup. In most cases the highest ranking commander on an army post is most often not the post commander. The guy in charge of the place is usually a full colonel, but there is usually a tenant unit whose commander is some level of a general officer. The philosophy behind that is that a general has better things to do than worry about roads, maintenance, housing, facility security, and other "town government" kinds of things. The generals run and/or staff the military units, and a colonel handles the "town government" and housekeeping. Overseas the position. at least in the Army, is usually callled installation commander.
US Parks: One big deal with the no guns in federal parks bit was that part of the highway system in Virginia next to DC runs through a national park, causing a lot of controversy because it turned a lot of legally carrying Virginians into criminals just by driving someplace they had to go all the time. That probably helped get it changed.
US Post Offices, VA property, and any other federal owned, leased, or tenanted property: No you cannot leave the gun in the car. You cannot even drive into the parking lot if you have a weapon. Including any knife, even a folding knife, having a blade longer than 4 inches. The law says federal "property", which the parking lot is, not just in a federal building. That's a big problem at VA facilities.
The VA medical facilities are most times miles, miles, and miles from many vets. In states with large rural areas, from most vets. I used to live over 400 miles round trip away from the VAMC that I had to got to every month. Now I'm closer, but it's stll 90 miles round trip. The same is true for VAROs, which are usually in the same city as the state's VAMC. And, especially in states where many vets are legally armed, nowadays pretty much everywhere except the Northeast and California, it is a horrible problem.
I was waiting to see a pharmacist yesterday and a VA cop came up and started asking me if I had a gun. I'd been talking about guns (rifles, actually) with someone and some ********* called the cops claiming she'd heard me say I had a gun on me, which I had not. I'm not that stupid. It
might have helped that he knew me and knew that besides being a vet I'm also a former large city cop, I don't know. When he questioned me he specifically asked if I had a gun out in my car. If I had, it would have been the same crime as if I had it on my hip inside the hospital. By the way, this stupid law is so broad that even currently full time sworn state, county, or city police officers cannot legally be armed on federal property unless they're there on official police business. Current or honorably retired LEOs can get a special permit from Homeland Security, but the last time I checked it cost $400.
As far as I know, no VAMC or VARO anywhere in the country has a parking lot anywhere nearby which is not part of their property, and I'm completely certain that if even any do it's a pay to park lot. Many VA police do utilize some common sense; one time a few years ago I was leaving and one saw me holstering my 1911 as I was getting in the car, and he just stopped and checked that I was on my way out. But he could have arrested me, and some would. Another time, going through the security screen at the VARO, noticing my empty holster, a VA cop asked if had a gun locked in the car out in the parking lot, so it seems to be official policy to enforce the no weapons anywhere on VA propery. If you have a weapon in the car you just have to hope that the VA cop who realizes it is more reasonable than the law is. Not a hope that it's comfortable staking your potential punishment and a permanent criminal history on..
The law as it now stands legally disarms all veterans who have to drive to a VAMC or VARO, every day facing tens of thousands of vets with the choice of either leaving all firearms and all knives with a more than 4 inch blade (even standard folding Buck knives are too long) home when they have to drive to a VAMC or VARO or being a federal criminal from the moment they drive into a VA parking lot until they leave. If anything happens, like maybe an accident on VA property, and they find a weapon in the car, the vet can and very well might be arrested. In fact, because of that I suspect it is open to a constitutional challenge, and I wish some organization with the necessary resources would sue to get an exception for securing weapons in the vehicle when a vet has legitimate business at a VA facility providing, as the federal parks rule now requires, that his being armed is otherwise legal in accordance with federal and applicable state laws.