I have a pressure tank in my garage which is, of course, connected to a tee
with the gauge and switch located very close to it. I would like to leave
the gauge & switch where they are but extend the 1" line going to the tank
about 70 feet. This would allow me to place the tank under my house in an
area where the "crawl" is about 9 feet high.

Is there any reason not to have the pressure tank so far from the switch?

I would also like to insulate the tank so it will not sweat during our hot,
very humid summers. What would be the best material for this? I do not
want to harbor mold so I would like to keep air from getting between the
insulation and the tank.

Many thanks for any help.