Esslemont grows a lot as a writer, Stonewielder is a huge step up in writing quality, though I love ROTCG despite its flaws.
Kazz didn’t suddenly appear, Skinner had buried him alive. The body Kyle found was Kazz, it just didn’t wake up until Kyle and the others had started back towards the boats. It’s written a bit so so, but that’s how it was.
Skinner was able to survive a fight against Dassem twice, hardly a looser, though a real psycho bastard.
Dassem Is Dessembrae "The Lord of Tears", so he hasn’t been human for a long time.
As you have discovered, the Esslemont books aren’t thigh in novels, they are important parts of the Malazan series on their own. A bunch of plotlines from Eriksson books were continued in ROTCG (Malick Rell, Laseen, Urko "Keeper" Crust" etc.) if you want the whole story you can’t skip them.
I’m currently 400 pages (of 600 total) into "Orb, Scepter, Throne" and it continues a ton of stuff set up in Eriksons TTH.