I could be wrong (often am) but it's my understanding you do Not want to over inflate your tires. If it says 90 psi, then you should only put in 90 psi. As for the axle issue, I can't much help you there but I know several women here wrench their own and/or others bikes. They might be able to help you better.
Goodonya for bike commuting tho. You might consider taking the bike into your LBS for a good going-over. Our shop will do a maintainence check for about $30, might be worth looking into just for safetys' sake.
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"