"A car battery"
As in 12 volt nominal "cranking" battery?
1012 / 230 = 5 amps
1012 / 12 = 85 amps
That might work.
http://www.howstuffworks.com/question219.htmAlthough I wouldn't try it with the battery still in my car.
If a problem occurs with the inverter or pump motor... well, there are probabilities and then there are possibilities.
Probabilities - A measure of how likely it is that some event will occur; a number expressing the ratio of favourable cases to the whole number of cases possible
Possibilities - The fact or state of being possible.
Even though someting will probably not happen it is possible.
All I can honestly tell you is what I might do, and that is, keep what you have for now and invest my money in a large, true deep cycle battery bank and a 120/240 inverter with charger. Then as time and money allowed, invest in PV, and or wind, and or water genny's. Gradually weening myself off of the ICE (Internal Combustion Engine) genny. Eventualy shutting it down for good one day or, at least having it ready for those short, gloomy days, one after another, during the Winter months.
As for sizing the battery bank and inverter. You would have make those calculations based on your power usage.