Depends how BB is constructing sqz range, if goes linear which is most common and good strategy we need to defend less than if it was HU because other player help us with defending.

I'd call mixed here, with something like 98s+, A5-A4s, A9s+ and expect to be playing vs range 88+, KJo(mixed)+, JTs+(mixed), some wheel aces and low sc(low freq).
About calling PP I'm not really sure, but I definitely don't want to call 100% of them: maybe 22(25%),55(over 50%), 77(100%)

p.s. I said for 100BB and assumed that BU is 100BB too, now it is all awkward and I'm not sure we should be calling much at all. If BU reshove and BB do same we can't go all-in with KQs for example. So maybe 4bet or fold and when call - always continue :/