1. I've almost always preferred tweeters on the inside. Lately they have been re-affirming the need for the tweeter to be a little (inch or) further from the listener than the bass panel for proper time alignment and that requires tweeters in with a little toe-in to aim at the listener. You can do it with them on the outside but toe-in tends to be less and I don't like the image as much. The only times I have had tweeters outside was in very large rooms when I was a fair distance away. Less than that, and it tends to sound impressive with a wider image, but never quite sounded "right" to me over time and I put them inside.
2. If Magnepan stated 8 ohms it is a typo; they've always been ~4 ohms nominal, with a little dip around the crossover points, and the ribbon tweeter drops to 3 ohms or below in most cases. Some are closer to 5 ohms, mainly the centers and smaller guys. They do spec at 2.83 Vrms without an impedance so the actual sensitivity is about 3 dB lower than typical. Not lying, but presenting "in the best possible light", to be kind. They do send most of their energy forward (and to the rear) and do not radiate much to the sides or above/below so at a distance are more sensitive than a conventional speaker that radiates much more to the sides and top/bottom. Magnepan's claim has been for decades that their radiation pattern (from the lower midrange up) provides them an advantage over conventional designs -- but they are still pretty durn insensitive.
The jumpers are there to make it easy to add tweeter resistors since for many folk the tweeter runs "hot" so they use the included resistors to reduce its output a little.
4. Audyssey, and may room correction programs, can get confused by dipoles especially if the rear wave is not damped. Maggies, like any planar speaker, have somewhat limited excursion (compensated by large panel area) and distort badly when driven by large bass signals. I crossed my MG-IIIa's at 70-80 Hz, an octave above their -3 dB point. That provided better bass and on up since the panels mo longer had to deal with large bass sounds. Helps the amplifier as well.
5. The wrench used to be to tighten the bolts/nuts for the attaching the stand. Embarrassingly I've forgotten what the cut-out end is for...
FWIWFM - Don