Buckets are notoriously leaky. I have some that will not bubble an airlock at all even in the most active phase of fermentation. That's okay, and the must will still ferment, but in order to know how it is going, you need to check the gravity. That is the most reliable way to measure the progress of fermentation.
As for the sulfur, 2.5 teaspoons of nutrient isn't enough and hungry yeast produce hydrogen sulfide (H2S) which causes the stinky smell. Yeast can also produce H2S when under stress from other things like pH. Adding a lot of acid to meads at the beginning often cause the pH to go too low, and can stall the yeast (and I usually recommend adding it after fermentation). Adding products like Fermax may move the pH up a bit and be helpful in addition to the nutrition they provide. If you open the bucket and stir it around to release CO2 you may blow off a lot of the H2S as well and that my help things smell better faster.
I hope it goes smoothly from here on out.
Medsen