I posted this on the DIY website because it is not plumbing related but I figured I get pretty good help here so why not try here too. This is a long-ish explanation so I appreciate any help I can get.

My house is built on Canadian Shield (rock) and on a slope. I have a crawl, about 6ft to bottom of joists on the downhill end which narrows to only a foot on the uphill end on one corner and about 4 ft on the other corner (land on one side of house is also higher than the other). After the house was built, they made an addition on the uphill side (a living room) by smashing through the crawl wall (literally). This area is about 2.5 ft high.

As for the finishing, there is nothing on the walls. There was white foam insulation (1"?) but I removed this to prep the walls for spray foam. Half of the original crawl has a solid base (either rock or concrete) and the other half is moist soil/sand. Under the living room is a combination of dry and moist fine sand. Where there is sand/soil there was a polyethylene barrier but it was thin and has since deteriorated.

For the questions:

I can remove some of the sand from near the walls in some areas. Would this be beneficial before I have the foam sprayed? There are areas where the inner sand level is level with the outside. What depth would be ideal to lower this to? Is it worth going through all of the effort to bring it down to the footings? (This would require removing 1 foot x 22 ft x 14 ft of sand for the living room area).

In the area where the crawl slopes up to within a foot of the joists, I had frost on the inside walls above the floor. I am assuming that this is because this area was not insulated well and the ground is so close to the floor. Is this correct?

In a few places, I can see that the wall ends and there is dirt/rocks underneath (sloping inward). Should I be pouring concrete up against this? Can I just spray foam over this? Should I do neither?

My crawl has my ducting, hot water tank and furnace in it, so I am assuming it is considered a conditioned space and should not be vented, but it has 3 vents in it (that haven't been touched in years). Any recommendations on how to proceed? If I close off the vents, what will happen to the moisture?

As in another post, my joists are set into the concrete. I read Gary's post here (Insulate basement header with imbedded joists???) but I couldn't quite understand if spraying the entire concrete wall and header space with foam would be fine.

Since it is moist in the basement, and drywall is not a good idea to "fire rate" the spray foam, is my only other option a "shotcrete" style coating?

Thank you,

Edit: I don't have photos at the moment but I will provide some if needed.