You mentioned that he lowered his head and chewed as if there was something in his mouth. There's different kinds of chewing. One of them is more of a licking and swallowing action that horses will do when releaseing tension that has built up in them, usually after being asked to do something that maybe they didn't want to do or didnt understand, and the handler had to raise the pressure enought to make the horse yield that tension resulted. The horse releases this by licking and chewing and swallowing. Some folks say that the horse is "thinking on" what just happened. Or soaking it up or whatever. Could be that he is and next time he'll do that action better and with less pressure. Pysically, I think he is just releasing pent up tension. We do it too; we may move our jaw and swallow after we realize that we've been holding it tensely.
The other jaw movement is not so much a sign of respect or yielding. That is clacking the teeth and crossingt the jaws. The horse moves the lower jaw way off to one side and back and forth and will make almost air biting motions and may clack his teeth together. That, to me, is a sign of resistance and tension, not relaxation, yielding or respect.
As for you and your gelding, when you start really asking for things from him you will be able to see how deep his respect for you runs. It's not like it's a light switch that is either on or off. If he has some respect for you at leisure, that might not be so evident when you start asking him to do things he doesn't want to.
For example, moving him off his feed. Making him leave the barn or his buddies. Canter if he's lazy, slow down if he's not. Stand quietly for mounting.
Things like that. Then you will see how strong is his level of respect. It really is based on trust, and trust is based on consistency in training.
Oh, I am sorry I am rambling. The usual , for me.