Hi!
I suggest you to lower marking for both User and CPU. That will give attackers more time with the ball without being pressured by defenders. Defenders will cover more the space and passing lines instead of constant man marking.
About GK: variability is a real life thing. Great Gk make huge mistakes and poor ones also make astonishing saves. The question is how often? I suggest you to start with a lower value and increase if needed.
Cheers!
PSN ID - Ric77pt