I'm certainly no expert, but I have Janet Hamilton marrying William Wallace of Elderslie, Renfrew (the Elderslie family). And there are a few William's down that line too.
Unless I've gotten my John's crossed, the 1st John of Craigie b. abt 1331 or thereabouts married first Elizabeth Eglington and 2nd Margarget Lindsay.
I'm guessing that you are referring to the family in Craigie primarily, and I agree with you, the dates are all over the place. There are so many different dates on the internet that it's very difficult to decide who's right and who's wrong. I have the John who married Margaret Cunningham (Cunnyngham) dying in August 1570 according to Rev. Charles Rogers in THE BOOK OF WALLACE.
The other John, I can't identify by the dates.
William b. abt 1513 I have married to Margaret (Margery) Sophia Kennedy. I show his death as 1538, again based on Rev. Roger's book on the Wallace family which can be extremely confusing because he lists very dates of birth or deaths, and in some cases I think he may confuse the Johns and Williams and who suceedes whom. Or I may be confused in trying to interpret what he wrote.
And I could not determine by the dates which William you are asking about.
Hope this helps. or maybe it confuses you more.