How would I convert 130 lb./1,000 sq. ft. for each inch of thickness to lb./ cubic ft.?

Answer 1

1 square foot X 1 inch thick = 1/12 cubic foot

130 lb/1000 square feet/inch => 0.13 lb/square foot/inch

So 0.13 X 12 = 1.560 lb/cubic foot

Which is actually pretty light - on the order of polyurethane foam, for example. By comparison, water is about 64 lb/cubic foot.