Yes, there are copies of the Shackleton Book still available for purchase. If you will email me privately, I will send information.
Regarding dates of birth of this Richard Shackleton - the Jan 12, 1760 date, as you said, comes from his Rev War pension file. The Jan 11 1763 date comes from info on his tombstone which says he died Mar 8 1839, age 76 yrs, 1 mo, and 25 days. Which is correct?....I don't know.