Roof sheathing

[dmarino55]

In 1988 manufactured double home, I have parallel 2x2's for ceiling (with insulation between) and then a growing air space gap from wall to roof of 2x2 supporting sheathing. Underside of sheathing is brownish (and flakes a little) (top of sheathing normal color), and when temperature changes (like this weekend warmer in Ohio) apparently lot of moisture that trickles down in brownish/water liquid in some areas of exterior wall. I have no roof vents nor ridge vent. At the exterior wall, while there is a vent, the space is blocked by thickness of the insulation I have no idea how far back towards top that are blocked by insulation, I would guess 3 feet.

At what point might sheathing need replacing?

What would you recommend to get more ventilation (I was thinking of putting black flexible 1.5" piping with holes in it from the vent about 4 up the roof cavity (drywall is off exposing are in soffit to shove pipe in)

I was also thinking of putting a couple small turbines 3/4 way up.

I was also thinkint of putting in ridge vent.