If you want to do it properly, engineer it properly - at the moment your running around in circles without any chance of ending up with a successful outcome.
For starters, you say toilet/s don't close off properly, you are bursting pipes etc - fix these issues first before worrying about changing the supply method.
Pumping from a tank directly into you system is the best way to go, it just requires to be done correctly with a no leaking toilets, / taps with the pump discharge pressure controlled to suit the pipework etc.
What model Hitachi pump do you have?