You have to overemphasize the initiation of the spin with the handle on the tramp. And, make sure to wait for the pop before spinning on the tramp. Also, make sure you simulate how you'll be approaching the wake (toe/heel) when you practice.
The symptoms that you described are caused by 1) throwing the spin too soon = off axis, 2) not pulling the rope through your back = losing handle. Try initiating the spin by pulling w/ two hands on the rope. Also, try a toeside 3. They're easier to grab the rope. Good luck, and don't get frustrated.
Flipping and spinning are totally different animals....I remember reading something years back about Gerry Nunn ripping it up until Shaun Murray teased him about backside 3's. Evidently, Nunn fell about 10 times trying those until the sun went down!!! And, as you can see now, Nunn can do it all...just takes practice. Don't become one dimensional. Its worth the effort to learn.