Hi ascanius.

Nice map and steady heading in the right direction, but there's one key thing about your text and map that makes me itch a little bit. (Now, as always, I am inclined towards accuracy and plausibility and you are free to ignore my ramblings and fantasize at will) . You seem to think of the continents as pieces of crust floating atop a sea of ocean floor, and that makes your placing of ocean ridges much less plausible and actually harder.

Have a look at this map. Do you think a similar map could be drawn given your mid-ocean boundaries? Not that you need to do it, but I'm trying to show that the placing of the oceanic ridge in the east (instead of roughly centered) is difficult to explain.
You could perhaps, instead of moving the boundary to the middle, create a second divergent zone in the west. And then, between the two, a deep ocean trench (which, for any purposes, would give a lovely set of very-far-away-volcanic-islands-at-temperate-conditions).

There's a second region where this inconsistency happens - the northeastern ocean. I don't know if you ever heard/read about the Wilson Cycle, but if you doing your tectonics from a "Pangaea to present" point of view, it wouldn't be a bad idea to have a look at it.