This is where I think some rythm beads (spelling?) would come in handy- to teach you to post and be in tune more with your horse.
He's actually a really nice jumper! He's got nice form and good scope for such a small jump- almost looks like he's jumping too early but not his fault- that's what you need to tell him- when!
Posting isnt that bad- to this day I count 1-2 1-2 because that's what my instructor taught me to do- I always sit the lope.
For the two point position you can practice by rising (two point) all the way up to the jump if you want (not all the way up out of your seat)-- I always drive my horse forward and rise as I feel the horse pull the front legs off the ground and sit after the backs have landed using my legs as shock absorbers-- you don't want to hollow the back or lean too far forward- the most comon flaw I see in jumpers is them poking their backside out and leaning too far forward-- it should be kind of natrual feeling not uncomfortable or like you're really trying to over do it.
I do agree with everyone- you need an instructor to help you and don't try anything you're not comfortable doing.