I agree with everybody's observations on this, an awesome update!
Jack could definitely sneak Parson through the portal the GTTMA is not careful.
And yes, Jack is definitely learning from Parson, but he probably always was something of a lateral thinker. To be a master class foolamancer must require a keen understanding of the limits in other people's thinking. It's just two short steps to applying that to yourself, and then to the world itself.
Then I thought of him stacking with Marie and Janice, and then I thought of how terrifyingly powerful it would be to three-way link a thinkamancer, a predictamancer, and foolamancer.
Any two of those linked could do some scary stuff.