I was wondering if anyone could help with how to time the jump for level 3. I just can't seem to get it right.

I guess your problem here is wrong movement pattern. As I posted in the guides, you need to JUMP from the crates for most things to work properly, and save some time across the game. To jump from a crate, hold the jump button while inside a crate (for at least ~1 second) then release. Double tapping to get out and jump from the crate is slower, and I think I used that only on levels 7/9.

As for level 3 skip, I don't have exact numbers or time, after many times of practice you just "feel" the right spot. Try jumping around the time the crate leaves the ground, and there is a split second you are in the air.

Even then, Lvl 7 and 9 can still implement this technique, reducing the total time by at least another half-second. I recommend being patient. While in the crate and going off the cliff, wait a split second. Do not try to rush it. I learned that the hard way.

Can you see yourself get out of the crate before you die? If so (and if you are double-tapping), your first tap is too early, and your second one is fine. You need to get out just after the crate passes the corner.