In zone 4A it doesn't matter which side of the assembly the vapor barrier is on, as long as there aren't vapor barriers on both sides. (Kraft facers on both sides would be fine, but not foil or polyethylene.) Vapor barriers aren't even needed at all, but if you're going to have one, putting it on the conditioned space "warm in winter" side is preferred. With any new construction or additions in your climate it's better to avoid true vapor barriers such as foil or polyethylene in wall assemblies, and use standard interior latex paint as the interior side vapor retarder.
It's also good practice to build out the siding as a "rainscreen", with at least 1/4" of air between the exterior sheathing and siding to promote rapid drying of the sheathing. (The ~1" air space of a brick cavity wall behaves as a rainscreen too, but you don't need it to be that deep for most siding types.) Vinyl siding is inherently back ventilated, and doesn't need a rainscreen for the sheathing to dry rapidly.
Very few homes in 1966 were built with foundation insulation of any type, and fewer still had exterior side rigid foam. Some brick clad concrete block homes of that era were cavity walls, many were not. In your case it doesn't much matter if it's a cavity wall or not.
If you want to insulate the foundation from the interior side, using 3/4" foil or plastic faced EPS (pretty cheap at box store) trapped to the foundation wall with a 2x4/R13 (kraft faced or unfaced) works fine from a moisture point of view year-round, both above-grade and below, and will beat code minimum performance (= R10 continuous, or 2x4/R13, which has potential moisture issues without the foam.) If you go this route, put a layer of the EPS under the bottom plates of the studwalls as a thermal & capillary break. The wall foam keeps the average temperature of the exterior side of the fiber insulation and studs on the above grade portion above the indoor wintertime dew point, thus avoiding wintertime moisture accumulation. The wall foam also impedes ground water migration (as either water vapor or liquid) from getting into the studwall too. The studwall dries toward the interior, all seasons.
An all-foam solution would be either 2.5" of EPS, or 2" of polyiso clamped to the foundation with 1x4 furring through-screwed to the foundation with 4" Tapcons. In many locations you can find reclaimed 2" fiber faced roofing polyiso for under $15/sheet, making this cheaper than a foam + studwall solution. With polyiso you need to keep the unfaced bottom edge off the slab, since (unlike EPS) it can slowly wick and store moisture, losing some performance. Even a half-inch of air is fine (or slip in some EPS and let it rest on the EPS, which doesn't wick water.)
The air in the garage is always above the dew point (of the air in the garage). The foundation walls and slab are often below the dew point of the OUTDOOR air in summer, and insulating the foundation walls won't change that, neither will adding a French drain. But the drain may limit the amount of bulk water that comes in contact with the foundation. Does the interior side have a history of water intrusion (real leaks of liquid) anywhere, or excessive efflorescence? Either of those conditions would be an argument for a French drain. If there is only a modest amount of efflorescence and it's only in the lower foot or so of wall digging in the drain isn't on the critical list before moving forward on insulating the basement.
The entrained air in the soil is almost always at or near 100% relative humidity at whatever temperature the soil happens to be. It's fine if the foundation is damp- you just want to limit the amount of moisture that gets into the living space. The wall-foam takes care of that, as long as you tape the seams and seal the top & bottom edges to the foundation with polyurethane caulk (not the cheap stuff) or can-foam to prevent slow convection of that 100% RH air in the micro-space between the foam & foundation into the room.
Putting a small register on the supply duct is fine, as long as you provide a return path such as a jump-duct or wall grille to the rest of the basement. It's better if you add a short length of hard-piped duct with a balancing vane between the register grille and main duct so that you can tweak the flow up or down, which may need seasonal tweaking anyway. Below grade rooms never balance perfectly with above grade rooms since their heating & air conditioning loads don't vary in the same proportion with changes in outdoor temperature.