B_Dub, you say it wobbles under 1/4throttle. sometimes that is normal, and it goes away when the blades find their lead/lag positions. check to make sure your blades are equally tight and see if the wobble happens during spindown also. go above 1/4 first till it smoothens, then drop below 1/4 to see if it's as bad as it was during the initial spin up. if it's smoother, during spindown, it's just lead/lag, which is not a problem in flight.

yes the dd tail will help keep the tail straighter when you are learning to hover, however it is much more prone to breakage during a crash. so i'd recommend staying with the stock tail until you can hover a few packs without a crash.

as you mentioned, the cp can be much harder to fly than the cx. just stay patient and stick to RADDs. you'll get there soon enough.