Schumann's sonata no. 2, first movement help

[piulento]

Hi there!
I just started working on the first movement of Schumann's 2nd sonata op. 22, and I have to say - it's difficult as hell!
I don't play Schumann often because I always found his music (while beautiful) quite awkward to play, and this sonata is one of the best examples.
So far, the thing I'm struggling with most is the fast left-hand jumps. I've played plenty of pieces with fast jumps, but never like this! It's almost impossible for me to play them correctly at the right tempo, and the worse thing is - if I practice them too much I start having mild pain in my forearm.
Does anybody here have some advice about good ways to practice the fast left-hand sections? (or any general advice about the piece - I'd really appreciate it)
Some examples of sections with fast left-hand jumps:
0:40-0:45
3:58-4:06
4:50-4:58

Thanks in advance!