Jack is so much fun because no matter the situation, he stabs. Even if it only makes his situation worse. I wonder what he had actually planned to do to Lord English as Spades Slick. As long as he didn't just happened to have a cueball themed knife, I don't think he would have gotten far.
Jack finds a way to Stab. I mean, English is immortal, but if you like, managed to crush his skull or something I bet he’d die. He’d come back because God Tier Inconditional Immortality, but I bet you could /kill/ the guy. Maybe his plan was to like. Tie him up like a big piñata and just stab him forever.