May well be that Elsie and Harold did not divorce but simply separated. Divorce was pretty uncommon in those days (the cost and the legalities of the time).
I certainly can't see a death so far for a Harold Stewart to fit with his approx. birth year post the birth of his last child with Elsie...and when Elsie and Charles were together having children.
Are you related to the Stewart side or the Austin side? Just wondering what his daughters said about him at the time of their marriages (if married). Given he was in the army at the time of his marriage to Elsie in 1915, his daughters' birth certs should include a standard occupation for him likely.
Monica