It is counter-intuitive but gas leaks will allow air to enter your shield gas system. You must ensure there are no leaks! Also, event the type of hose can make a difference, only use a high quality impermeable hose material, do not use the cheap rubber hose.
I agree with Lawrence completely, on all the points he made.
Your 45 cfh flow is way too high, more is not better in this case, it will create turbulence that mixes in surrounding air.
Use a gas lens! If you want to overkill it, try a "Monster Lens", see http://www.arc-zone.com
As for your question on stick out, if your still having shielding problems, keep stick out to a minimum.