kW Rating of emergency generator for sump pump
You seem to have answered your own question: you need a generator with a minimum running current of 11 amperes and a minimum starting current of 43 amperes.  To be safe, I would suggest getting a generator with minimum running/starting ratings of 15/50 amperes. Assuming a 120 volt system, as implied in your question, the corresponding wattage requirements are 1800/6000.