He got them by touching a very powerful juju

It’s doesn’t have a ton of stuff on it yet but here you go.

I believe it’s Karkat: Contact John

That’s not counting the note that John sent to Karkat before entering the yellow yard.

He became a ghost.

The image for, I believe the 2011 Homestuck calender for the month of March depicted Eridan crossdressing. He is also shown wearing the outfit in the Ministrife flash.  So to answer your question, kinda both.

Not between just the two of them. They both speak in two different memos.  But they might have spoken to one another in one of the walkaround flash games.

I’ve read through it about 2 and a third times.  And I’m planning on reading it again once summer comes around and I have more free time.

Gamzee left it.  We can tell this because he used the blood of a void player (Equius’s) to cover up every mention of himself in the book.

There’s a wiki page for that

If a person god tiers with another life (Jade’s dreamself in jadesprite) then the other life is made the main life so Jade’s consciousness was transferred to her  Jadespriteself.  John’s body stayed on his questbed when he god tiered as well.  I’d imagine that someone buried all the corpses over the three year gap. As for why you’re asking so many questions, it’s because homestuck is confusing as shit.