I'm no expert on these things,but I was doing what your doing,and with your aims in mind.
I'd buy a 40lb bow,60 inches long.
#1 your not trying to kill anything.
#2 after shooting FITA your going to find 3D distances so close it will feel like your tripping over the targets,,so you sure don't need heaps of power to reach them.
A 60 or 62 incher should be both smooth an forgiving at your draw length.
But again, your not shopping for a hunting bow so why not 66.
I personaly have a 68" recurve I've shot a lot of 3D with.
The transition from sights and clickers to full barebow.
Unless it's against the rules in your local 3D,you can still use a clicker,lots of guys use those limb mounted types.
Aiming,,,well the best 3D shooter in your country (maybe the world) shoots instinctive.
Vist his web site and read what "he" has to say about that before taking any advice from anybody else on that particular subject.
His play on it is a bit different from most folks that shoot instinctive and he has a very easy to understand way of explaining the how's and far more importantly,,the why's of it.
Your going to have to look around a bit on his site before you find what I'm talking about,but it's there,it's not hard to find, and once you read it for yourself,You'll see what I mean.
All the best.
ED.