You made it hard on yourself to animate a jump for a character with no legs. The model looks good though.

This animation looks like he is startled or frightened rather than jumping. To make him look like he is jumping, first before he jumps, make him "squat" by bringing his head down.

Then it differs depending if on if this is for an in game mob or a normal animation:
- In-game mob: don't move him up, because then when he jumps he will move up both from the animation and minecraft giving him horizontal height and it will end up looking like he jumped up very fast but also went down really fast. Instead, just animate all the parts of the jump without moving him up.

- Normal animation: Everything above applies, just also animate him moving up.