How do you progress from small jumps to medium jumps? In the park they look drastically different and much higher?
The trick to bigger jumps is that a lot of it is just getting the speed right. They look scary, but it's the same jump technique you use on smaller jumps, you just want to make sure you make the sweet spot on the landing.
For me, I always watch a few people hit the jump and watch how many speed checks they do, how big/heavy they are, how clean they make the landing etc. etc. to judge where I should drop in from to get the ideal speed.
When you have 2 jumps in a row like that, the way to get the speed right is to first watch people hitting the first jump to figure out the speed, then ride up to the second jump and watch people hit the 2nd jump after landing the first jump. This way you know how much speed they take from the first jump to the second jump.
Doing it this way means you'll have to skip the jump line once to ride through, but it's what you have to do if you want to know the speed for hitting the jumps in a row. As you found out, going straight from one jump to another doesn't always give you the ideal speed, sometimes you'll need to do a speedcheck or some edge rolls.
As already mentioned, I'd recommend hitting the first 2 jumps in terrain garden on Blackcomb instead of Whistler. Those jumps are roughly the same size and ideal for learning jumps and even spins.