Of the 3 dates supplied, 3 Oct 1670 fits best between the adjacent children. 30 Mar 1670 (12 months and a week after Thomas' birth) is not impossible, but less likely than 3 Oct 1670. 3 Oct 1671 is too close (less than 8 months) to Rebecca's birth (26 May 1672).
'Will of THOMAS ORMSBEE of Reho., Yeoman, dtd. 3 March 1715/16, recorded 10 Dec. 1716. Wife Mary. 5 sons: Thomas, Jeremiah, Jacob, Ezra & Daniel Ormsbee. 4 daus: Mary Salsbury wife of William Salsbury, Hannah Thompson wife of John Thompson, Bethiah Shaw wife of Thomas Shaw & Esther Redway wife of Preserved Redway ... [3:316/7].'