Settees
There are three; mothers, smother, and thermos.
Using all 7 letters you get rewords
Seven letter words that can be made from those letters are shutter and stretch.
Sinkage is the seven letter word formed using the letters aeigkns.
essayed
deleads
sellout
demotic
wavered
There are no seven letter words from these letters.
An eight letter word with three vowels using those letters is scavenge.Eight letter words with four vowels using those letters are agencies and envisage.
No 7 letter words there. 5 letters is the best you can do: arena or anear