The town of Millstreet is in Drishane civil parish just to the north of Clondrohid civil parish. As you have determined already the Millstreet RC parish records do not begin until 1853. That parish is also in the Diocese of Kerry. There was a chapel in Millstreet in 1837 and I'm sure well before but the earlier records were lost. See this excerpt from the Lewis Topographical Dictionary (the RC info is at the end of the article).
It looks like the larger number of Tuohig families were in Clondrohid parish but your family migrated north to Drishane at some point. If you check the Tithe listings http://titheapplotmentbooks.nationalarchives.ie/search/tab/index.jsp there were a number of Tuohig leaseholders in Clondrohid and none in Drishane parish.
The 1852 Griffiths Valuation head of household listing shows a Honoria Toohig in Mill Lane in Millstreet and I'm Wondering if that is the mother of the family before she emigrated?
You don't mention DNA testing but you may want to consider a test. You may come up with some third cousins.