For question one, have a look at this.
Display the degree character in Micro python? - Discussion - Pimoroni Buccaneers
For me its mb and I just divide the Pa by 100.
pressuremb = pressure / 100
Have a look at this example for the Pico Enviro+
It has code for gas readings, correction for MSL, and temperature compensation.
pimoroni-pico/micropython/examples/pico_enviro/enviro_all.py at main · pimoroni/pimoroni-pico (github.com)