Donald J. McIsaac Jr., heir to West Marin’s golden era of dairy and cherished husband, father and friend, died on May 11 in Sparks, Nevada. He was 70 years old. Mr. McIsaac was born on August 29, 1941 to ranchers Lorraine and Donald J. McIsaac Sr. His Swiss-Italian great-grandfather had established the family’s Tocaloma dairy . . .