Didn't even read all of that but a pretty common cure for 'balancing tanks problems' is to install a small reversing pump in the line between the two tanks, and then plumb a short line bypassing this pump with a shut-off valve in it. Sometimes you might want to pump all the fuel from one side to the other and have it stay there - shut the bypass valve, switch this pump to pump to the tank you want. When you want to 'balance'
again, simply open the valve,