Can this pull down attic ladder be fixed

For the 50:50 rule, I don't see the ridge vent becoming an intake unless there is another second ridge vent. So given the choice, I'd ignore the 50:50 rule unless your ridge vent is not at a single height.

That said, in your specific situation, with a strong wind from one side and the soffits closed on that side, I think you're creating a situation where regardless of how big the ridge vent is, you could get a down draft from the upwind ridge vent to the downwind soffits. But more importantly, by closing some soffits, you are reducing the airflow under part of the roof. In areas of heavy snow, this airflow is critical to prevent heat from the home from melting snow from the upper part of the roof and having it refreeze on a lower part, forming an ice dam that would backup water into the roof (rot) and possibly into your home (leaks).

Because of the ice dam risk, I think you're better off going with shirlock's earlier suggestion to rely on the Styrofoam tunnels stapled to the rafters and adding some ridge vent filter to any soffits you are worried about. Then install a ridge vent of the proper size for your roof.

The stairs should gain access to the attic in such a way that:

1) one has max. headroom,

2) the attic stairwell doesn't prevent access to any part of the attic,

3) the stairs permits a path of travel to a ground floor exterior door (ie. doesn't come down into the hallway in such a way one would have to close the stairs to exit the bldg.)

4) the stairs would not likely require furniture to be moved to be used.