***** NOT A TEACHER *****
1. I believe that you are 100% correct.
a. I believe that for the sake of analysis and in order to use the wonderful Reed-Kellogg diagramming system, we
would have to reorder some words:
i. All that ends well is well.
(a) "All" is a so-called indefinite pronoun. (Although one expert * asks "What is indefinite about" it?)
(b) "is" is a linking verb.
(c)"well" is an adjective that refers to "all." (And as another book ** says, "all" often means "everything.")
(d) Since we know that it is a lie to say that in this world "All [everything] is well," we have to qualify "all."
(i) In other words, all/everything that ends well is well. (An adjective clause that modifies "all.")
[After analysis and diagramming, you can change it back to its customary order: All is well that ends well.]
Hopefully, Mr. Antonson will find time to draw a diagram for us.
* Dr. Paul Roberts, Understanding Grammar (1954), page 85.
** Dr. Randolph Quirk et al, A Comprehensive Grammar of the English Language (1985), page 382.