Found my first Wormhole

[Reprisal]

So I had about 1.5mil worth of unallocated skillpoints so I put them towards a buzzard with decent probing skills so I can scan out hidden asteroid belts during hulkageddon. First thing I found was a wormhole, so I entered, stealth and scanned around for a bit. Found a few sleeper cells but don't have to ships to mess with them yet. I found a really nice asteroid belt I was thinking about mining at but had a couple of questions. I found the wormhole in a .5 system about 11 jumps away from jita.

1. Will sleepers attack me randomly while I'm mining at this asteroid belt?
2. How likely is it that a player will find and gank me while I'm at this belt with 2 hulks and an orca?
3. How long do wormholes generally last and what happens if it collapses while you are in it?

ps. If anybody wants to join me let me know, the character I'm in the most is Repraiter.

Edit:
Ok, spend about an hour in there probing stuff, sleepers do randomly warp to the belts, in sets of 4 for this wormhole. Didn't engage them so I don't know how hard they hit. There were 5 really nice asteroid belts, 2 glass clouds and a bunch of cells of npcs. Turns out the wormhole closed while I was in there, took me an hour to probe out another wormhole that took me to a system 15 jumps away. So it was fun getting back. I think I might load my hulks into my orca, then go in with that and two ravens and see what happens. I might have to keep one in a raven for the rats. I'll keep you all updated if you want.