Hi all needed your thoughts on what to do here.

Live in California and have an at-grade crawl space 30×30. I’m doing an encapsulation and have mostly finished it. Vapor barrier down and have insulated the studs that come down to the concrete foundation and have a dehumidifier set up. What I’m left with though is the side of the crawlspace that is next to my front porch. The studs come down to the foundation but then there is a narrow 5 inch gap between it and a cinder block wall that is holding up the front porch. At the bottom of the gap is dirt. I was planning on using foam board insulation between the tubs be seal the edges with foam to essentially seal off the crawl space from that gap but am worried about humidity up in that space during the winter and the effect on the studs.

Thoughts on how best to handle this?