Hey JABBARA
Your Questions 1-2:
Think about it. if the leak is in the outer tank (is higher than inner tank) and you split it you do not allow the fuel to go to the inner tank (which is lower and possibly under the leak). Other way around if the leak is in the inner tank and you split it you keep the fuel away from the leak and use it through the stby pump.
Question 3:
Consider your question again while reading my above answer.
Question4:
Possible but not likely!