As Ellen was also born IOM I would assume it should be Kissack.
The Baptism 12/9/1841 is strange , normally you would expect a baby to be named by baptism time.
The age does fit in by 1861 , but in 1851 she was Mirra and aged 8.
Her sister Margaret was shown born England on 1851 and 1861 Census , so the family must have spent time in England.
What is the time and place of George's second marriage ? Have you checked deaths in the UK ?
Cheers
David Dwyer
I am in Sydney