Parallel wiring may work and is permitted under certain circumstances, usually much larger services where multiple smaller conductors are easier to install. but I'm not going to advise this as both conductors for a phase must be in the same raceway, I hardly think this will be the case, however...
The pumps I've used I cut the hose, slipped it over the pump outlet and hose clamped it.
Your solution may vary. Don't undersize the pump.... 1000ish gph mag drive would be my suggestion.
One might have a suddenly different view of things were they to become disabled through a stroke or illness.
People are people, we all deserve a life. I'm not religious but I can see that compassion is an important part of the human condition.
Best is to utilize a hydrogen fuel cell to store extra watts as hydrogen seperated from water. One can easily upsize a hydrogen storage vessel and lifespan is greater than traditional battery technology.
That said, Rolls Surrette or Trojan deep cycles are the most commonly used by off griders.