Really, I don't quite know how to answer you question about the long swing.. I would just teach a glide, even if it is a little piked for right now... You can always elongate the swing later.. or do what you need.. this is one that you will just have to be creative with.
As for the pulling/pushing question - I still suggest you just think of the kip as a swing. Swing from the basket to the support position, and those questions will answer themselves. It isn't like a kip on a single bar - you should end up with your hands past your hips, which would normally be impossible with a bar in the way, so the pressure is constantly downward from the get-go.
With therabands, depending on where you have them set up, I would do conditioning for straight arm pull downs, like the arm action on a kip. If he can do the kip on high-bar, he probably has the strength required for the kip on p-bars, and all the therabands will be doing is re-enforcing the action without added load. If possible, he should keep pressing as far behind him as possible so that his hands are behind his back.
From a basket, swing with a spot until he feels the "open" action and use that natural motion to help open for the kip. It's a swinging skill, in my opinion, a lot less than a strength skill. If he can compress well, and turn over completely for that basket, the swing will carry him and he will feel how to increase the energy needed to complete the kip. Then it's a matter of pushing the bar behind him and keeping his hips up (again, something that will come with learning the swing motion, and conditioning positions).
Practice the positions, and the skill will build itself. I think the finishing of the kip is the hardest part, seeing that you need to swing out of it, and the tendency for most learners is to drop their feet down once they feel pressure on their hands.
Maybe Im just not explaining it clearly... maybe another coach will chime in and give their opinion on it...