Expresso, Pipeline, Lower Oilcan, Crinkum Crankum/Kirkford are all comparable in difficulty to Pangor and Severed, and how all those trails rank will be somewhat subjective. Ladies has some tougher sections but, as stated, is probably the most interesting trail to ride and will still be fun if you have to walk some sections. If you're doing well on the Seymour trails, it sounds like you have the skills to attempt any of those on Fromme.
I say go ride them all, and ride them again. Familiarity helps a lot, and you will probably ride sections you previously walked the second or third time down.
Also, don't neglect the lower trails like Floppy Bunny, Bobsled, Natural High, Immonator and Griffen Switchbacks. Those are great warmups or runs to tack onto the end of a ride.