possibility for Teresa's 2nd marriage from the BMD Index :
Name: Teresa Craven
Registration district: Dublin North
Event type: Marriage
Quarter and year Apr-Jun 1883
Volume : 2 / Page: 481
Also on the same page is a Terera Butterley, and a John Sheridan. Second marriages often listed maiden surname and surname from any previous marriages, and indexed under both.
It's the right area for Santry, and fit's with the children's births listed in the other thread. If it's correct this further narrows down the timeframe for William's death, making this one the most likely :
Name: William Butterly
Registration district: Dublin North
Event type: Death
Quarter and year: Jan-Mar 1878
Reported Age: 44 (est. year of birth 1834)
Volume: 2 / Page : 448