Agree with sarahvr.
There's absolutely nothing wrong with either piece of equipment used separately or together, but I don't think you're going to fix any of your current issues with tack.
A pelham can be a wonderful choice of bit, with a lot of flexibility, when ridden correctly with two reins by a rider who understands the function of the bit.
A horse that throws his head is 1.)either uncomfortable with the bit in his mouth or 2.) highly resistant due to lack of training or poor training. My approach would be to get the horse's teeth checked and then work to find the best fitting/most comfortable bit possible, then embark on a program of flat work designed to increase acceptance of the bit. I'd take a similar approach to bucking - eliminate pain and soundness issues first, then saddle fit issues, then flatwork and lots of it, concentrating on really getting the horse out in front of your leg. Riding a buck defensively really only works in the short term, the long term fix is to ride forward.