I have done similar work.

I found a floor scraper at home depot to be the sturdiest option.
Also used a big drywall sander, then a little bit of skim coating.

Most outdoors electronics/equipment enclosures I have seen just use a thermostatically controlled exhaust fan to keep temps down.

Knowing if you are in a heating or cooling dominated climate is helpful here.

You want your thermal barrier and air barrier at the same boundary.

If you insulate the floor the space below will certainly get colder. Would the pipes be in the spray foam? that might be safe enough in terms of freezing. Do you have a sense for how cold it gets down there currently in the winter?

If you insulate the crawl space walls then you will want to seal up the vents to the crawl space.
Moisture is a concern, dehumidification can get expensive. An exhaust fan on a humidistat might accomplish what you need at a lower operating expense.

Since you have pipes and ducts down there I would seal the crawlspace and put in mechanical ventilation and or other moisture control.

Wow, a lot of bad information here. You cant really go to school for home building so information gets passed down...

You want your thermal barrier and air barrier on the same surface. Previously that was the attic floor, now it is the attic ceiling.

The heat from the whole house is rising up through the vents, and that is pulling cold air in down at the low points.

You want to seal the vents. It might not be a bad idea to install a fan to the outside up there that can be sealed or a bathroom exhaust fan. Your house sounds unlikely to become too airtight, but if it did the answer is controllable mechanical ventilation.