We are also investigating a link between James Kirkpatrick of SC and William Kirkpatrick of PA.
There is a batch of Kirkpatrick settlers in New Castle Co., DE which is adjacent to Cecil Co., MD. In between the Kirkpatricks who lived in DE, MD and West Nottingham, Chester Co., PA, was a Welsh settlement (Pencader) which included Presbyterians.
Some of these Kirkpatricks married Welsh families. A group of Welsh subsequently moved from New Castle to the Conestoga Valley (Caernarvon Twps in PA), possibly suggesting a scenario where James lived temporarily near Reading, PA (asserted by websites on James): That settlement was 14 miles from Reading.
However, the movement to Conestoga was second generation. James would have been connected to these families back in vicinity of Pencader, possibly through his wife.
History books mention that New Castle settlers migrated together to the Carolinas before James arrived there.
I'd like to know about your Mitchell family. We suspect that our William Kirkpatrick may have had a wife who died young.