Working on my first system [HELP]

[Syrphid]

Noobie here. Just putting together a small set-up to experiment with, and I have a few questions that desperately need to be answered.

Just picked up a 15 gallon tank, wondering if this 4 gallon bin (top of tank) is going to provide enough water pressure required to drain correctly using the flood and drain technique with a bell siphon.
To keep a vacuum inside my horizontal drain pipe, how long should my pvc be between my vertical drain and my fish tank considering how small my build is?
When purchasing a pump, how many gallons per hour should I be looking for? (Will be hiding the pump under gravel)