Yes, airing it out will affect the proof. You will lose more alc than water but sacrifices have to be made. My rum tastes ok after the first run at about 65% (diluted of course). But a 2nd run is worth the expense & might fix your flavor problem. The cuts can be made much easier on the 2nd run also. 2nd run for me, at about 80-83% cleans it up & after diluting to 40% still has a sweet smell & is better than anything you can buy. Sorry, lose the aluminum, there must be an alternative.
Keep trying... it will get better with experience.