advice on sealing crawlspace vents to outside air
If you seal the crawl space the humidity can rot wood and cause corrosion of metals. I had a similar house in northern IL, I guess it may have had more humidity. When I bought it in the 70's I added vents because the joists were black in places. There was also corrosion in the galvanized electric boxes in the house. My crawl space "floor" was just soil.