Thank you for writing to me. You ask great questions. You have a big pool in a location that has unpredictable spring and fall weather. A 100,000 BTU heater is sized correctly for you pool with a blanket. The liquid blankets are better than nothing. If a regular blanket keeps 100% of the heat in at night then I think the liquid will save 20% of the heat. You must turn the water pump off at night or the liquid blanket won't work as the water movement breaks the surface tension and you then lose heat. In MI I like to run the water pump from 8 am to 8 pm so that the heat pump will run during the warmest part of the day. Then you will get the most heat for the money that you spend on power. So to answer your question, if you want the most possible season then get the biggest heat pump that you can afford, and if you want to start heating the pool the earliest possible moment in the season and go as late as possible or you want to heat at night because some power companies give a break on the electricity rate then get a heat pump that will defrost like a Jandy, Rheem or Gulfstream.
Most people are fine with the heat Siphon that goes to the low 40's as if you are getting below that temperature during the daytime then probably you won't want to swim much.