It's difficult to pin point which Robert Callow.

Indeed it is; there were several Roberts apprently. Thank you.

1. Did he die 1837 and was his mother Anne ?
I don't know.

2. Did Eleanor remarry to Thomas Mylecraine ?
Yes, and she was married to Robert Cannon before Robert Callow.

3. Did their son emigrate to Wisconsin ?
According to my research Thomas Mylecraine & Eleanor emigrated to Wisconsin (Grant Co, 1856). Whereas, Robert and Margaret (not sure where or when he married her or what her maiden name was) emigrated to America in 1860, and ultimately settled in Idaho City, Colorado. I have an 1880 Census that has the family in Idaho Springs, CO (Robert, age 43).

4. Have you any additional information ?
I have an excerpt from a book "A Pioneer Family" by Sarah Quirk Arman that simply states "After the death of Mr Cannon, his widow, Eleanor Q. Cannon, married a man named Callow, and they had one son Robert, who after sailing a number of years, went to America and settled in Idaho City, Colorado. He had one son and two daughters."

Len Faragher