Fantastic write-up.
I think you're mostly right, but I think that the Unmade are collectively the counterpart to the Stormfather/Nightwatcher (instead of just Ba-Ado-Mishram).
My personal theory is that the Unmade were once a single entity that was shattered/unmade into the entities we have now. I think that this "Made" would be your bondsmith spren. As to whether bonding Ba-Ado-Mishram would result in a bondsmith now? Brandon has said bonding one of the Unmade is possible. I would be interested to see what happened.
The coppermind and Hessi's Mythica think that Ba-Ado-Mishram was unmade:
https://coppermind.net/wiki/Ba-Ado-Mishram
The Unmade are collectively parallel to the Stormfather/Nighwatcher:
Unmade (much?) less powerful than the Stormfather:
Unmade (and presumably "Made") can be bonded...
...but have not been
The unmade were something before they were unmade (not necessarily a single something, though):
Symmetry is definitely a huge thing on Roshar, religiously and otherwise, so an Odium bondsmith (or at least the spren) makes a lot of sense, and is my main reason for thinking that the Unmade used to be a single entity (to closer match the Stormfather/Nightwatcher).