Wall assembly recommendations CEI to older home Zone 5 – GreenBuildingAdvisor

I’m adding continuous exterior insulation to a 50 year old home in zone 5a. I work for a rural Habitat for Humanity affiliate so budget and accessible materials are challenges. I need a little help confirming if I’m on the right track with the wall I’m working with.

The house has 2×4 walls with fiberglass so I’m assuming R-13 at best, then plywood, board and batton siding (minus battons) and 3/4″ xps. My plan was to add 2″ xps over the top with 1×4 strapping using 6″ screw (I welcome affordable screw rec’s) but my main question is about the WRB. My understanding is that at this level of insulation I could go with a class 3 vapor barrier like house wrap (which we have donated). Is that correct? And it goes between the furring strips and xps but over the window bucks right?

One more question about the vents at the top. How does the rain screen assembly vent at the top of wall? I don’t see any details about that. Thanks so much for your help!