Thanks! But yeah stuff I've already known about the Calling. Unfortunately, where I live stores don't sell Dragon Age merch. And our postal service here is so abysmal I don't dare to order anything online. Haven't seen any digitals on the books either. That theory does seem reasonable. Do we know anything else about the Titans? It could explain why there are only seven archdemons. The Forgotten Ones' souls are trapped in the red lyrium? But where is the Calling Song coming from then? It can't come from the Old Gods (assuming they are not tainted to begin with) so is it coming from lyrium surrounding the Old Gods?
That sucks. 
There's a lot of theories about what the true reason for the Calling is. However, the Old Gods themselves do emit a Calling. A pure, untainted version of the Song. The Wardens attempting to preemptively kill the Old God buried beneath the Western Approach witnessed the Song being so powerful it could be heard physically, and likely caused a cave-in. Old Gods got some lungs. Once tainted, the Song becomes twisted, but it's still hella powerful.
All we know about the Titans is Kieran's comment to a dwarf Inquisitor about how they 'can't be taller without the Titans'. Cole at one point discusses something that the dwarves were cut off from that misses having the dwarves, with the nice little wham line 'You sell it,' to ex-lyrium smuggler Cadash. I'd recommend you find a video of it, as I'm sure I'm losing a lot of the juicy context.
The theory I mentioned earlier wasn't that the red lyrium was the Forgotten Ones/Titans, but that lyrium in general was, and red lyrium was the Blighted Titans. Think of it as cancer specific to a part of the body. Hence, the Profane Codexes in the Primeval Thaig in DA2 about how 'they devoured the gods'.
Between the Primeval Thaig and the temples alluded to underneath the 'modern' Deep Roads in The Calling, it's obvious dwarf religion used to be different. We've got scraps of information to puzzle over for now. 
As for your comment about the Archdemons' number, I'm not sure I understand.
If the theory that they are the elven gods holds true, then it's seven plus the two gods not trapped that we've already met.
EDIT: WOAH WOAH WOAH, Dirth Enansal, hold the phone! Motivated by Qunari?! YOU MUST LINK ME TO THESE CODEX ENTRIES! ESPECIALLY ABOUT THE MAGISTERS' BELIEFS. I'M NOT SLEEP DEPRIVED.
I only found the Three Darkspawn and Claw of Dumat Codex entries. Share your knowledge!
I do think you're onto something with the statues. The weird dragon statues present in Crestwood were also in the Brecilian Ruins, which seemed to be a mixture of human and elven elements. There's also been speculation that June was a dwarf, just going off his different size in his pantheon profile picture and the white coloring suggesting a beard. Still pointy-earred, though. It's possible some dwarves worshiped the Creators. It's possible some elves lived underground.