Find out what's knocking your chain off. Since you have the bike and workdstand, you're better equipped for finding the problem than we are.You can simulate riding under load by holding back the rear wheel while working the crank on the stand. Find out what's knocking the chain off. Since it only happens on the big ring, I doubt it's the chain. Make sure the derailleur is aligned according to spec, 1-2 mm above the big ring, with the outer plate parallel to the chainrings. Check for a bent ring. Check your limit screws. Check for a bent derailleur plate. And, yeah, while you're down there, you might as well check for a bent or sticky chain. And, of course, along the way, somebody might have buggered the chain line by installing a bottom bracket that was too long.