If you see green leaf (and you really should see two small round leaves) then it's going. In my experience it takes a lot of punishment to kill a sprout that is showing green. A common issues I see with sprouts is that they have trouble sloughing off the seed casing to fully open their sprout leaves. If the casing is above soil on the stalk for 24 hours and I either don't see green, or don't see a full leaf or two worth of it, I take fine tweezers and see if I can softly remove the casing myself. You have to be careful, if it's not ready and you pull to hard you can rip those precious leaves inside, but if it's ready it should slip off at least one of the leaves fairly easily. Though it can take up to 10 days (a figure I heard and have read a few times), my experience is that if they aren't poking through the soil after 3 days from cracking, the odds of them making it go down significantly. Personally I suspect rot in these cases, and this is part of why I stopped using paper towels. I soak for 12-18 hours, and then plant in well moistened soil with lots of peat and fine perlite, then put them under 24/0 of T5's at around 82-88f. I have had much better success than when I do more manipulative methods of germinating.