I think I mostly understand the arguments behind the Shartan theory, but for whatever reason just can't get on board. Solas-as-the-dread-wolf-and-
surprise-also-as-Shartan-andmaybeaspiritorsomething basically seems a bit much to me. I could certainly be wrong, but it just feels too far-fetched to heap that much on one character.
Not to mention the potential negative reactions to whatever these things could imply for the romance in retrospect. I feel like the writers would want to stay clear of any fan fallout that could arise from those added complications. His revelation as it stands is pretty shocking, and some people are already upset with the way everything has ended so far, and were questioning the validity of his feelings, and whether he was using Lavellan, and so on. It would seem a risky (and lazy) gambit to go far beyond what they already have with him.
I'd like to think that I'm self aware enough to separate my desire for Solas and Fen'Harel to be uncomplicated and one in the same from these discussions, but it could be playing into it, so I won't discount it altogether.
That being said, I think it's been confirmed that a lot of the banter between Cole and Solas are references to films, as is some of Cole's individual banter. So, in these instances it seems the writers are kinda toying with us a bit.
Regarding Solas speaking of his childhood and not considering the pantheon (or himself) to be gods, I don't think this lends support to either theory, really. It just is. ¯\_(ツ)_/¯
I do find the idea of elves originally being spirits or partial spirits joined with a non-spirit intriguing and wonder if maybe that's the case with some of them (hence Solas saying "or something we haven't seen" among the options he lists for what the gods "could" have been), but I just can't get a clear enough idea of the mechanics surrounding this to think it would be the case with all of them. I'd like to read more on this theory, though.
When it all comes down to it, I really don't know, and wouldn't be massively surprised if they did continue to throw us curve balls regarding Solas. It's all just considered suppositions, for me. It sure is fun to discuss, though.