I'm no expert, but I think that it may help to lift off a bit before because it seems you hit the edge before you've actually reached the full height you could get. I think sometimes that your rear wheel hit the pallet in the middle, which should probably be avoided.
The height your pedal upping is an annoying one in my experience, I'm in a similar situation where your jumping a respectable height and you've got the right basic technique but it's harder to improve. Just try to remember and emphasise preloading, kicking harder, making your own body jump higher and tucking in towards the end.
Also, I've found it helpful to learn to wheelie to pedal up to improve my technique. I don't know if it's just me that it helps but might be worth a try, I suppose.