A: Most likely, yes they can. There is always "fine print" associated with airline fares and they can charge different amounts based upon the time of day, day of the week, % of seats filled on the flight, etcetera.
A: Unfortunately, since there is no signed contract, the verbal agreement is not enforceable. Try to work out something with the landlord to get a few more days time in exchange for the time and labor expended cleaning up the house.
A: A personal injury attorney. If you did not become physically ill, require medical attention or psychological counseling, your recovery won't be a whole lot. A personal injury attorney can explain the details.