I'm not sure we can answer your questions, especially the details you're looking for. The first one for this forum would be if it's Matsumoku made; I have no idea.
The first challenge with these old Japanese guitars is making them playable. Nut, truss rod adjustment, fretwork, neck angle, anything you can do with the bridge. If you've got that right, then worry about the pickups.
I'd start at 1/8" below the strings and see what it sounds like. Then up or down to taste. Too close to the strings might cause too much magnetic pull and cause warble or "Stratitis".
For the magnetic questions, I'd go to a forum like:
https://guitarnuts2.proboards.com/board/16/pickups I think I'd try the pickups as-is. You could try the old screwdriver test- stick a small screwdriver on the poles and see how hard it is to pull the screwdriver off vs. some other pickups. Then hold it just above the poles and compare how strong the pull feels.
If the pickup wires go through the top of the guitar, I'd mount them where the pickup wires seem to fit best. The 5.77K pickup might be for neck position. If the pole spacing differs, the wider pickup would be for the bridge.
No way to know who actually made the pickups or how many variations there were.
-Steve W.