Unless you have a very low LOT, I´d say start with
BTC for the fastest gains.
As for
weight, I´d say try 3 pounds first and hang for all available time divided in sets. If you don´t reach fatigue, move up in
weight slowly. Maybe you will move on to 5 pounds in a couple days, but give it a try first and see how it feels.
Anyway, from what I have read you are gaining very fast now, I wouldn´t change anything yet, but it´s your call.