I doubt a self tacking jib set-up could be used with a standard jib, they probably have too much mast overlap. A barber hauler could be rigged quite cheaply to sheet the heady closer inboard.

There's really no use for a vang on a cat unless you plan on sailing very wide angles downwind and need to sheet beyond the traveller, the vang will then hold the boom down but you really should be sailing tighter angles, tacking down and sheeting the main to the traveller. The kite will generate better apparent wind angles and allow you to sail deeper while sheeted tighter.

Your downhaul is an important control, there to alter the drive position and depth in the sail and if you're sailing it too tight you are flattening the main, moving the drive aft which can be slow in certain wind strengths while beating, and definitely slow off the wind.

I'm just now rigging the 430 with a kite using a f/glass w/surfer mast as a pole and it looks ok so far but could be just a tad heavy. I bought the mast s/h in the local trader.
Hope this helps,
Bern