IGI has James Killop marrying sarah Collister at St Luke in Liverpool on August 12 1844. Jame's father is given as Thomas and Sarah's as Paul.
I cannot locate a James of the right age with Thomas as a father. The IGI fas a Sarah Collister christened in Malew on Jan 20 1812 in Malew, daughter of Paul Collister and Judith Waterson.

In 1851 they are at Court Lion Street Liverpool HO107/2181 Folio 63 page 211.
James Killip Head Mar 30 Carpenter b IOM
Sarah Wife 28 b IOM
Sarah dau 5 b Liverpool
James son 4 b Liverpool
John son 1 b IOM
James Corless Visitor mar 56 Porter b Ireland
Josph Holton Visitor Unm 49 Mariner b Warwick
James Sharp Visitor 19 Unm Mariner b IOM
Thomas Clements Visitor Unm 20 Sailmaker b Liverpool
George Preston(in) visitor Mar 39 Mariner b IOM

In 1861 at 3 Court Lion Street Liverpool RG9/2674 folio 59 page 27.
James Killip Head Mar 40 Shipwright b IOM
Sarah Wife 45 b IOM
Sarah Jane dau 16 b Liverpool
James son 14 b Liverpool
John son 12 b Liverpool
Ann dau 10 b Liverpool
Thomas son 8 b Liverpool
plus five boarders all from the IOM

in 1871 at Court Lion Street Liverpool RG10/3776 Folio 86 page 62.
Sarah Killip Head Wid 56 Lodging House Keeper b IOM
John son Unm 21 Ship Carpenter b Liverpool
Sarah J dau Unm 25 dressmaker b Liverpool
Ann Elizabeth dau unm 19 dressmaker b Liverpool
Margaret C Kaighin Neice 5 b Liverpool

In 1841, Sarah Collister was a family Servant age 30 at St Anne's Street Liverpool HO107/559/25 folio 22 page 5.

Given the emigration to the US, the dates of birth and christening, the marriage in England, and the wife's name (Elizabeth), the Whitehaven Thomas looks as good a bet to me.