As far as silver bordered rules care, do the foil Siege cycle cards (and foil Crux of Fate) have both the KTK and DTK watermarks? Or is the shifting watermark considered its own watermark?

It has both watermarks.

Re: Italics-less foils; so can we infer that it doesn't take the same herculean effort to sneak a watermark onto a card for its foil? Crux of Fate and the Siege cycle from FRF had those Khans-Vs-Dragons watermarks on them that aren't present on the regular kind.

Every time you see a card that is different in any way, that was a new card that someone had to lay out.

You chose the one art I could find that shows Bolas shaped like a quadruped. Based upon every other art I can find of Bolas and Ugin, I genuinely thought they were meant to be bipedal humanoid dragons. Even ignoring his original art, Crux of Fate, Wit's End, and both his planeswalker cards make Bolas' forelimbs look like arms. I'm not trying to be contrary, I'm just confused.

People seem to be confusing “can be posed like a humanoid” with “humanoid”. The Internet is filled with people who dress up their pet and stand them on their hind legs to look like a little person. That doesn’t make them humanoid. Yes, Bolas has often been posed in a humanoid pose. I keep acknowledging that. My point is that a dragon is not humanoid no matter how often you pose them like one. Now there are Dragon people that occasionally show up in fantasy. Dungeons & Dragons has some. They are human-sized and have definitive arms and legs but have dragon features. Those are “dragon humanoids”. That is not what Bolas is. He’s an actual full/sized dragon.

in "crux of fate" is Sarkhan literally deciding to destroy all non dragon life on tarkir???

No, I was just making a joke in my comic contrasting the story to the literal rules text. The “dragon vs. non-dragon” represents the two future paths Sarkhan has to choose between.