got his head down, & when you pull it up its a matter of seconds before its down again, he likes to buck, I'm going to look into poll pressure & see if that does anything for us
DO NOT put poll pressure on a bucker! You will make it a thousand times worse, I promise you it is the worst idea out. That includes all gags, all curbs, anything that isn't a snaffle. If it has leverage, it has poll pressure. And poll pressure encourages the head to drop, which is the opposite of what you want.
The bucking, can you stay on it and remain balanced? If so, PUSH HIM FORWARD. Bridge your reins against his neck so he can't get his head down, and push him forwards. The best thing you can do for buckers is to ride through it.
Your bit does not have to be a plain snaffle. I personally will never put anything twisted in my horse's mouth but slow twist is an option, or a Dr Bristol. Try a thin smooth snaffle, even.
Training is key here. This horse has some BIG holes in his training which need to be fixed. Try remouthing him, or if you don't know how, send him to a trainer. I can't reiterate this enough - TRAINER TRAINER TRAINER. If you don't know how to fix a problem properly, you have to be willing to find someone who DOES.
99.99% of "horse" problems are actually rider problems, either current or past. My gelding for example once had a reputation for being "extremely strong, dirty and dangerous" but he's exactly the opposite, he just can't cope with heavy hands or riders who don't use their seat. Monty is incredibly soft, honest, and safe, for a rider who uses hand only as a last resort and is able to ride with a light following contact or a looping rein. [BUT, he does need a rider who CAN be quite er, firm with their hands, to back up their seat/light hand aids, because he CAN be a wee bit strong at times... but he's certainly not dirty or dangerous. As much as necessary but as little as possible is the approach that works best with him.]
So. Trainer, coach, TRAINING. Get him back in a snaffle.