My loose end is Johnathan STEVENS Snr UEL, whose daughter Elizabeth was married to Lt Frederick DACHSTADER or DOCKSTEADER (of Butlers Rangers during the American Revolution) She wound up in Ontario on UEL lands, but what happened to her Dad? When did he die? and who was her mother? Because Johnathan Snr was raised partly at Mohawk Castle (Canojaharie in the Mohawk Valley) I suspect she was probably Mohawk, but can't find confirmation yet.
Have you looked into the family of Jonathan Stevens and Lea Van Slyke in New York in the early 1700s? Lea was the d/o Cornelis Van Slyke and his Mohawk wife Ots- Toch. I have written 2 books on the Van Slyke family which included the descendants of Jonathan and Lea but stopped in the mid to late 1700s. There is a Jonathan Stevens who fought during the American Revolution, who was a descendant but I have no other info on him.
Have you hunted for the land petitions for these individuals? Loyalist land petitions often contain a wealth of genealogical. See the Loyalist section of Olive Tree Genealogy website for more help with Loyalist Research, also The Loyalist Institute has an incredible amount of free Loyalist data
Jonathan Stevens Sr was in Butler's Rangers (or Forrester's Interpreters) and is noted on the Old UEL list as having a wife and 4 children in 1786 so it is almost certain there is a petition or petitions on file for him. There should also be one for each of his children, including Elizabeth, if they sought land grants as sons or daughtersof a Loyalist (SUE or DUE)
I'd also get the petitions of each of his children as you never know if one might contain their mother's name. I think you'll find that Aaron Stevens, also a Loyalist in the Home District (which is where Butler's Rangers former men for the most part settled) was probably a son, and this fits very nicely with the names found in the Jonathan Stevens – Lea Van Slyke family. (Arent=Aaron and they had a son Arent bpt 26 Jul 1702 in Schenectady)
I see from Reid's book on Loyalists that John (your Jonathan) had a dau. Mary whose OIC date is 23 Nov 1816 so you can look for a petition filed for her around that time, also Elizabeth's OIC is Aug. 1796. Reid's book should not be considered the final answer to Loyalist families though, so be cautious using it - just use it for clues to help you along in your research
Here's a very nice candidate for your Jonathan, especially if he went by the name "John" - Nicholas' brother Johannes Stephens (Johannes=John) bpt 21 Jul 1736 in Schenectady. Johannes/John's parents were Arent Stevens and Maritje (Mary) Hall. Since your John/Jonathan named a daughter Mary this is a nice theory for you to prove or disprove.