Re: At wits end...help needed!!
Hi, I agree with doing all the basic checks first to make sure it's nothing to do with pain. It could be pent up energy, but some horses also change with lack of handling because they begin to think of themselves as topdog (and this often makes them more insecure). If you want to build up on his trust and manners first, I think that may help (it'll also exercise his brain), then I have a really good book 'Perfect Manners' by Kelly Marks, that I swear by!
If you want to lunge him, you can start by desensitising him to the whip. Have you ever seen a Monty Roberts demo? I think there may be a couple on youtube. He usually uses plastic bags, but the principals are the same. You can then lead him into the arena on a lunge line, and work in pressure training him, basically getting him perfect at leading (If 'Perfect Manners doesn't work for you then try 'How to Train Your Young Horse' by Robert Maxwell. It is aimed at youngsters, but works on any age!) so that he goes backwards, forwards, sidewards etc at the slightest aid. You can also use pole work (but that can be tiring so never for long) to get him thinking about where his feet are going.
Then try to lunge him, by lengthening the lunge line so you are a few feet from him, and ask him to walk around in a circle. Keep it simple, and if he bombs off, then let go of the rope, and wait for him to finish. Walk quietly up to the rope, pick it up and start again. Eventually, he will calm down and realise what you want from him, but I would definitely keep him in walk for the first couple of times.
Hope any of this helps, and that you manage to sort it out! Best of luck.xx
P.s forgot to say, you don't need a whip for lunging - body language is often enough - but I would still try desensitising him anyway!