1. In my experience ATC is a good idea gone bad, provided you have enough altitude it will work better, in most cases it just makes you loose control over your plane, it will shutdown the engine and apply some up elevator, in most instances if you are flying low, or trying to avoid an obstacle it will result in a crash, however you can limit the rate of the elevator/ruder by disabling the lower sensor and using ATC. Just use some dark tape over the lower sensor (like electric black tape), this way it will help not to over control the plane without the risk of having your motor turn off and loose control of the plane.
2. I only use factory battery, they are cheap and you can buy them on most local HS, I have 3 and that provides a lot of time.
3. By moving the control rod to the inner most hole in the clevis I believe is enough rate and aggressiveness to fly and perform any "acrobatics" possible on the Phantom.
Search in youtube for some videos from a poster called "NightFlyyer", he is a real pro... and you will find the he flies stock, and is able to do some very cool stuff, even rolls.