Replying to Mediocre at park! Tips?

Since I can't afford to take a mountain trip this year, I set a goal to improve my skiing here in ManiSNOWba; that means stepping up my park game.
Thing is though, I'm rather average in the park at the age of 23, even though I've been on twintips for 6 years now.

Popping is one of my weak spots.
I can slide rails, but currently only if the jump's at rail height. There's a 30ft rail at Springhill that I'm scared shirtless of hitting because the jump is half the height. The fear of injury is a big demotivator for me. At the same time I hate that I can only hit 1/2 the features with confidence. So how do you pop higher? How do you hit rails with a half height jump? Or one with a gap between the rail and the jump?

I can't 360; or rather I haven't landed one yet. I can 180, but then kinda stop. I don't get how to spin while carrying enough speed to clear a jump. Do I prespin? Do I use my skis?

That's all I can think of right now, but if I can think of more I'll post it here. So really what I want from you guys is just some advice on how I can get better. I've always been two steps behind my brother and I want to close that gap.