I haven't come across your type of wheel so this is based on the ones I've met. I've only actually changed one freehub, mine have all lasted the life of the wheel, perhaps I'm just lucky!
Looks as if the spindle (axle) is stuck. That should come out from either end. I'd try taking all the nuts, bearings and bits off the other end and see if it'll come out.
The freehub itself, if it's like the one on my son's old bike, will have an allen key hexagon inside - not sure what size it was but my kit only goes up to 12mm so it can't be bigger than that - I put the allen key in the vice, put the wheel onto it, and carefully turned the rim, which removed the freehub with very little force needed at the rim. I used one from a wrecked wheel to replace it, and that was a bit more difficult as I had to clamp the hub and use my piece of pipe on the allen key, but still not a problem
Edit: Just seen the link in the post a minute before mine - that's very similar to what I dealt with, but is a more upmarket hub with better bearings. The principle's the same though.
