dig out and finish my crawl space into a basement
Please use extreme caution if you proceed. This is not a job for an amateur. The back-fill dirt you are standing on in that crawl space is part of the engineered structural integrity of the entire house. If you pull too much of that dirt out of the wrong place, you can compromise the integrity of he foundation.  You don't want to go there.  This project can be done but you need an experienced builder in this type of construction or you need an actual building engineer to do the necessary calculations and provide drawings.