RE:yellow yard

Some carapacians saw it in a cloud, so it was always going to happen. Hussie the character wants them to cross the yellow yard for the same reason Hussie the author of Homestuck wanted them to, to fulfill a piece of foreshadowing.

Why did Snowman tell Terezi to exile Jack Noir? (pg. 2532)

I'd like to give a different answer than what's been provided. I mean, maybe she would have done that anyway for that reason, hypothetically. The actual reason she did it was to fulfill a time paradox, because of course she's already working for Doc Scratch at this point. If Snowman didn't step in and instruct Terezi, Jack's original plan of taking BQ's ring for himself would have doomed the trolls' session. More importantly, if Jack Noir isn't exiled, Spades Slick doesn't kill Snowman.

How was PM able to resist/attack Jade? Why couldn't Jack do the same? (pg. 8087)
I'll add onto Danya's point by mentioning that by Collide, Jack has already gone through his "killing people is boring" phase, and his "I'm really sick of running from this chick" phase. I think that small section he has in the dreambubble, reliving the events of seer: descend is the closest he ever gets to character growth. Not EXACTLY regret, but more like... futility? Which is something of a theme for the carapacians. It's not just that PM has a stronger motivation, but that as early as act 5 Jack's motivation has already begun to wane, and by the time he faces off against PM I doubt he wants to go on any murder rampages at all.

What is Jack's Real Name?
I mean its just Jack, right? If you mean his alliterative "SS" title, as per the default parameters of Sburb, then we just don't know lol. Maybe... Sepulchral Statesman?

Who "Commissioned" Bec Noir to destroy all B universes? LE? Is he afraid? (pg. 5072)
Yes, it was Lord English exactly. I think LE just believes its poetic for Jack to execute his plans, since that's how he originally won against Calliope. This is why B2 Jack gets possessed by English, Caliborn just likes him.

How does Calliope have Doc Scratch's gun/holster/wand?
I think its more accurate to say that Doc Scratch has Calliope's gun/holster/wand. Its a trophy that Caliborn keeps, which is why Lord English immediately reclaims it after killing Hussie (cosplaying as Calliope's OC).

Why does CD blow up the Black and White Kings? (pgs. 4703 & 4704)

To subvert the mechanics of Sburb and give Condy more control over the session

(Possible Continuity Error?) How did Hussie pull out the wand after tossing the magnum? (pg. 4804/4807)
I can't go back and check, but it might just be Eridan's wand. That, or the idea of the magnum and wand being one in the same was a retcon. I don't believe it ever transforms between the two before Calliope is introduced

Where did the Ring of Life come from? (pg. 6034)

The white queen. The ring of life and void are just WQ and BQ's rings before being prototyped.

Why did Kurloz take Vriska's pirate coat? (pg. 6066)
I think it was a setup to establish how the cairo overcoat was created, but its never followed up on

Why did LE leave his gun/staff behind? (pg. 6116)

He doesn't really need it. He can kill way more people at the same time just using clockwork majyyks, plus he replaces it with the wand

How did Caliborn turn his black gun/staff gold?

Alchemy probably

Why is The Cueball necessary to create a weapon capable of harming Lord English? (pg. 6322)
Something something hoisted by his own petard. In all seriousness, it may just be part of his bargain with yaldabaoth