Poor little guy. I’ve never seen that before, but agree that it looks like he’s gagging on something…like maybe a feeder got stuck. How big are the feeders that you gave/give? Does he chew his feeders or just gulp them? His feeders shouldn’t be any larger than the space between his eyes. I prefer giving ones that are on the smaller side and just give more of them. I’m assuming he’s stopped making the noise and body heaving. Is there any wheezing, popping or other sounds coming from him? Is he holding his head up, like stargazing? Are his respirations really prominent or do you have to look carefully to see him breathe? If your credit is decent, most vets offer care credit. Asking friends or family for help may be an option. Once this episode has passed, you may want to consider pet insurance for him.
I can’t be of much help with the specifics of Jackson’s husbandry. I don’t know how fast they grow, but he does have some pretty sizable horns for being a juvenile.
I do hope your handsome little guy will be ok.