As far as all of those issues go,
Barrel Whip - if you were talking about a bolt rifle with a free floated barrel, this would probably be more of a valid/issue or concern. However if you are talking about a semi-auto, the other things attached to the barrel (gas block, gas tube) will also impact the barrel behavior. I am not aware of anyone who has tried, or been able, to "model" this behavior to a point that they were building rifles based on that information.
Bullet Exit & Bolt Movement - not sure if you have read this:
http://ar15barrels.com/prod/operation.shtml
Hate to say it, and don't take it the wrong way, but are you pretty much trying to "reinvent the wheel" or trying to build an "enigma wrapped in a conundrum"?
Grab whatever barrel length that works best for your application,
Short - better handling, positional shooting, closer ranges
Longer - bench or prone shooting, longer ranges
Go with the longest gas system that will work with your barrel length. Longer gas systems operate smoother/better.
Then build/tune a handload that works optimally with that setup.
By tweaking your pressure & velocity in your load, you will be able to match that with your barrel and gas system performance for optimal results. This is the "way that business is done".
Best of Luck,
M Richardson