#1 cup makes it easier to do armbars (sicnce you get a LITTLE extra leverage from the cup), but it's not always necessary, i almost never wear a cup when i grapple, only wear a cup for striking
#2 you roll so the choke gives you more leverage
#3 do a can opener or wait for them to do a submission, they will let go of teir legs eventually, or, like others have said, dig your elbows as hard as you fracking can into their legs, they'll eventually let go, or, grab one of their arms at the wrist first and stand up, then push down on one of their knees to open up the guard.