I had a lot of trouble in cups always facing active higher levels until I followed Nikos guide how to win the treble. It won me the cup last season and unlucky in CL and League. It's worth a shot. Also, you're not shy on quality so maybe more attackive formations might help?

Strikers are having goal droughts unless they're chasing counters or lethal from freekicks but I still feel they act like a false #9 pulling defenders away so they're not a total waste.