Grampy only spooked (pulled back) at one occasion when I tied him, and that was when I tied him for quite a while to groom and saddle him... He pulled back and seemed terrified, so I just un-tied him, dropped the rope and he stood there and let me saddle him w/o any trouble, just like if he knew how to ground-tie. That was the only time I even noticed any "trouble". So my theory is that either he is borderline claustrophobic, or he got trapped/caught once before and couldn't free himself, or he just had a horrible experience in a trailer being tied (it is hard to get him in a trailer at first, but once he is in, he is just perfect).
With the mounting issue - we were out in the open and I used a plastic step-stool for mounting, and every time I put it next to him, he slowly moved away a little (just enough so I couldn't get on....LOL) - we did that maybe 5-6 times, and then I got on w/o incident. And the dismounting was similar - he walked right up to the stool, but not close enough to make it easy for me to get off. The next time he did the same thing, but it only took me maybe 3 times to get on. So I think if someone could hold him while getting on, or if one could get on with the help of a fence or something "natural", I think he would be just fine. And even with a stool, I'm sure with a little getting-used-to, he would drop that habit quickly....
Hard to figure out what causes his reactions - I know he has been neglected in the past, and I'm fairly sure he was abused as well, but he is a very, very sweet and affectionate horse....
Here is the one incident that made me believe that he was abused: I don't ever use whips or anything like that, but I do have a "Parelli training stick", and when we had trouble loading him to go to his foster home, the hauler said "go try a whip", I said "I don't use whips, but I can get my Parelli stick"... So I went and got the stick out of the tack room, and the second Grampy saw it, he jumped into the trailer - before I even waived it at him.... I felt so sorry for him - he probably left here thinking that I was going to hit him - that still haunts me......