Why would that happen? Not every failiure has the same effect.
Again, they're not supposed to realize you're counting up successes and failures. They're just trying to accomplish a thing as a team and you track their success and failures to help you know what the consequences would be.
I'd ask them to describe what they are doing that requires them to be Stealthy and what they want to accomplish.
What are they trying to do? And again, they shouldn't know that stuff.
Well now that's just a classic murderhobo
Well to be fair a Wish would be something the PC could do.
I don't see what you mean no? If nothing happens for 5 minutes, you have officially taken a short rest and the encounter is over. 4e is very much non-ambiguous about its durations and I don't know why you keep hammering on that point?
Okay? then they can just use bypass the challenge by spending the ability to fly.
Yeah they were badly explained and it's pretty difficult to make a good one because sometimes you get to the end and realize you forgot to come up for a situation where the party fails. Like I said, the best way I found is to just not tell the PC 'you are in a skill challenge'.
I don't think they expected you to read the Power/Item Lists like a novel. I think I never read a class power list beyond like... level 3 encounter powers until I reached a specific level.