12v 100 watt panel will give about 8 amps if my math is correct. So if I have a 200 amp hour battery, not going over 5% of the charge would be about 10 amps, correct?
I think you are asking about load. You can load your battery as much as you want, e.g. pull 100 amps for an hour. You understand that shortens the battery life so you are hoping to pull less from the battery. I agree with the people who said to get a generator, specifically for the well pump. I also agree with the people who said to get a cistern (or equivalent storage) and pump the water from that with a small 12V pump when the power fails. YOu can get the 12v pump from an RV supply outlet.
If you just want to get through a day or two of power failure, go with the generator. If you want to turn to solar and batteries for day-to-day use for small loads (e.g. computer, internet, small TV, even a small fridge or DC freezer), then do it and you will have part of what you need to get through the power failures.