Yep, looks good.
Also, I had
Breath Detector. The giant culicid is exquisitely sensitive to the chemical composition of the air, and can detect and locate creatures that breathe within a range of 300 feet.
from somewhere - given how good mosquitos are at detecting breath, would be good to...
ok working on it...how's this to start (modelled off tabanid) - NB: already a 'giant mosquito' statblock in licenced content so will need a name change.
Okay, coming back to this one...the splitting concept makes it like a vaporous ooze - but splitting after feeding rather than after being hit by lightning. This is a pretty unique mechanic in 5e and so I think is best as next cab off the rank.
Also making its CR different to the other two misty...