It sounds like you are quite inexperienced & have a young, uneducated horse. Therefore, the most helpful piece of advice I feel I can offer is to find someone as soon as you can, who is experienced, to teach both you and your horse! While you can learn a lot from writing and videos, there is a lot that is missed without hands-on help.
Regarding feeding treats for training, I'm of a very different opinion to most here obviously. Horses learn very well to do what works for them, from *instant* consequences, whether from reward - a gift - or from pressure and release. *However* if you do want to feed treats, you need to have definite, consistent rules for behaviour - you must teach your horse to have 'good manners', or else yes, he will do things like try to nip you, if he thinks that might work. So...
You need to work out what 'manners' he needs to learn, to be safe and practical. For eg. teach him to keep his nose tucked away from you. Regardless of whether your horse has done something 'good', you NEVER, EVER give him a gift if he doesn't keep his nose away from you. You can also use 'pressure'/punishment, such as the above suggestion, to make it unpleasant for him to do Wrong, which will stop *the instant* the horse moves his nose away, but it is most important that you don't ever allow that behaviour to work for him.
You also ask how you can teach him without 'gifts'. Pressure/release is the normal way to teach a horse to do almost everything, regardless of whether you also give him rewards. It is how they learn to move in a certain direction from the reins or lead, or from your legs when you're riding. The horse feels some pressure/pushing, until *the instant* he moves in the right direction, when all pressure is released - stopped, you don't keep pulling/pushing. For your example of jumping(I am assuming the horse has learned how to be led with pressure on the lead rope), you might start on the opposite side of the jump and pull the rope. As soon as your horse starts to come forward, you relax the pressure, so he learns what works for him.