The first thing I'd suggest is to change the coil to a new one. I find that, when my coil is getting gunked up it tends to make me cough.
If you're vaping less and getting cranky, then try a juice with a little more nicotine in it. That will give you the same amount of nic while vaping less that you got when you were vaping more. Does that make sense?
Good luck, and let us know if any of this works for you!