I don't know much about atonal writing, but I did enjoy it. Comparing it with pieces I have heard by Shoenberg and Berg I can agree with Sojar that the rhythms seem more simple than I would expect from an atonal piece. Also I'm worried a little about your timpani part. There are many different notes located close together, some of them chromatic, and I'm not entirely sure how playable it would be. I'm sure it could be pulled off with pedals, but it would probably end up sounding muddy. Just a thought.
In general, you've convinced me that you understand atonality well enough to use it and still create an enjoyable bunch of sounds. A lot of composers (myself included) don't have this skill, so congratulations.
It depends on a few important factors. Namely:
1) The lung capacity and diaphragm control of the player: If you cannot sing the line without running out of breath it is likely the player cannot either.
2) The length of the instrument: Long instruments require more air. It is important to realize that for woodwind instruments changing the pitch is effectively synonymous with changing the length of the instrument, so generally speaking it requires less air to play in the high register (speaker keys make this a little more difficult to estimate). I believe that brass instruments require equal air throughout the overtone series of a given fundamental - at least this is what personal experimentation leads me to believe, I of course cannot reach beyond the first few partials and must admit I do not really know.
3) Air pressure: Conical instruments require more air pressure because they are narrower at the tip. This makes them harder to play but it also means that air enters the instrument more slowly and therefore that they can generally play longer. Oboists for example are very rarely in danger of running out of breath, but rather of running out of oxygen - the air they inhaled becoming saturated with carbon dioxide. IANAD, but I can hold my breath comfortably for 60 seconds, so I would think you can with good conscience write passages that last maybe 30 or max 40 seconds for the oboe. You would however be highly optimistic to hope for a passage half as long from a contrabassoonist.
I hope this helps, somebody correct me if my information is wrong or inaccurate.