Subvisual Haze

I imagine soulcasting blood is a lot like Stormlight passively healing wounds in general.  There's a template of how things "should be" in the cognitive realm and the magic works to replicate that into the physical realm.

Jasnah is probably preforming a rudimentary form of hemodialysis when she is soulcasting blood.  Take out a certain non-lethal volume of poisoned blood -> replace it with "normal blood" (using Shallan's cognitive image of a healthy self to guide the Stormlight/Soulcasting of what her usual non-poisoned blood would be like).

Just like with dialysis or normal glomerular filtration of your blood by your kidneys this would be a time consuming process and require multiple "cycles" to progressively cleanse the blood as you can only remove and filter a fraction of the total volume at a given time.

Endowment is spending so much time peering into the future and simulating possible outcomes that it has manifested on the Cognitive as a future simulation Nalthis? 

I'm guessing the position of the anomaly corresponds to the point in the near future that Endowment most closely watches (as future prediction becomes less accurate the farther in the future that you go).  Something less than a quarter rotation, or greater than 3/4 depending on which way things are spinning?  So something like 2 or 10 months into Nalthis' possible future.

regarding Kelsier and his lack of (or backwards) character development: I think that might actually be by intent, indicating that current Kel (Cognitive Shadow likely stapled into a new body) isn't a perfect copy of original Kel.

While a really close copy, I think you "lose something" when you die and keep going as just a cognitive shadow.

Gotta disagree with you on Moash's Bridge 4 Tattoo fading because he has changed.  I think it will have the exact opposite significance.

Kaladin and Marsh are reflections of one another.  Both are justifiably angry and passionate men who have had incredible injustices done to them by the world.  Kaladin had Syl though to act as his light and save him from a downward spiral of empty vengance and self-loathing.  Moash will probably need Kaladin to fulfill that role for him.

Just as Kaladin can't quite escape the darkness he bears towards lighteyes, I predict Moash won't be able to forget the kindness and redemption that his time in Bridge 4 offered him no matter how hard he tries.  Much as Kaladin's slavebrands have refused to fade, I think Moash's Bridge 4 tattoo will prove just as annoyingly persistent.  They're yin and yang to one another.  Kaladin's a creature of goodness with a taint of darkness he can't let go of (the slave brands), Moash's a creature of darkness with a mark of redemption that will stay with him (bridge 4 tattoo).