I realize this is an old post. Have you been able to stop him from chewing on cross ties? You can try making them a little tighter, but it won’t stop him from chewing.
I am letting a young lady board her 10 year old horse at my place. My and her horse are fed at the same time and in the same area. As soon as her horse was done eating, he would walk over to try to eat my horses food. I would stand there and gently push his nose away saying “No” each time he tried. After a couple weeks, he learned that “No” means you can’t eat the other horses food. He still walks over to clean up the few morsels my horse has dropped out of his mouth on to the ground and occasionally tries to get away with sticking his nose too close. As soon as he hears “No”, he just gathers what’s on the ground or walks away. Whenever he walks away, I give him 1 treat, but no more.
Good luck and let us know what worked for you!