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I'd suggest putting your fingers in the pressure point under her jaw and push her head up, then bridle with one hand. Eventually she'll stop, so long as you cn prevent her from doing it. If she learns you can stop her, then she won't try any more. However, just pulling her head up and yelling, she's like "yeah? Well, I can still do it, see!"

so.. .yeah xD it's the same with picking up a horse's foot. If you want them to stop jerking it away, hold on.

Well, I only skimmed threw the first half of the first page, so I have no idea if this has already been said or not but, here is it:
Before you get on Sammy, make him 'soft'. Stand just behind his girth and pull on one rein. Keep the pressure steady, and maybe pet his girth a little. Once he gives, release. Keep doing that on that one side till you can get him to touch his nose to his girth. Repeat for the other side.
Then, while you're getting on, hold both reins, but make the left rein WAY shorter than the right rein, so that Sammy's head is bent towards you. Then, get on. If he tries to run away, he'll run in circles and eventually get sick of it. It shouldn't take him too long to realize that trying to run off isn't going to get him anywhere.
As for him pulling the reins out of your hands...Hm...I'm assuming you use split reins? Try using not split reins...I don't know....I've never really had that problem before. Well, we did have a horse that would swing both reins over to one side of his head though.....that got annoying.

Hi first off how old is this horse Sammy sounds like he needs more training.
I wouldn't lease him out to just any one I'd find a trainer for him,before leasing him out these issues can be worked with.Before you start mounting him if you have a lunge rope lunge him in a 20 meter circle for 20 min in both directions counter clock and clockwise so he gets the idea he's there to work don't mount him right away do this for several weeks every day this way he knows your not just going to mount right away get to know him.When you mount and he takes off grab him back and make him work in the circle again on the lunge line if this takes half an hour do it.Let him know this is not acceptable behavior.When you mount and he tries to bite you pull his rein the opposite direction away from the place he's biting at. At the same time tell him No in a stern voice. Horses are thousand pound animals they may be strong but are very awesome when you become the leader not him. Durring the process of lunge and other work outs when he does good let him know Durring training or any other riding and working with horses it's very important you leave with him on a good note meaning no stress no hitting no whips if he does good on the lunge line for half an hour or even 20 min brush him groom him love him then put him away let him know that is a good thing eventualy he'll get the idea that hey this isn't so bad.