Mmmmm nobody else has replied yet...must all be out riding!
From what I do know, that plastic dohicky with the grub screw and ball valve is used by BMW to fill the system at the factory. They do not go from the reservoir down and then have to bleed the system. Theoricaly you could take the whole thing right off and cap the hose, that is if you can find the right plug. To bleed the system you would have to pump the clutch then unscrew the plug , let air and oil out , retighten the plug without releasing the clutch, and repeat until the system is flushed.
I do not know if you damaged the ball valve trying to get the Grub screw out, but maybe only debris got stuck in there. Try pushing the ball valve in a few times with something small all the while putting slight pressure on the clutch to force debris out , it might clear it,then try bleeding by using the ball valve to release the oil instead of a bleeder.You will need an extra set of hands to do that.
If that grub screw is still in there, take the whole thing off, cut a slot across everything with a hack saw, going down into the grub screw enough to put a flat screwdriver in it and try that way. Putting the thing in boiling water might help to free it too.Sometimes trying to screw in first then back helps breaking the seal, you might have to do that a few times.
I just finished bleeding my bike and put everything back together, otherwise I would have tried bleeding with the ball valve to see what happens....too late....! I've seen other posts where they had problems with the grub screw......and do not like the $39.00 they want for that piece of plastic....!