Sadly I would say yes - meaning to keep your hub in good shape you’ll want to 1) stop trying to use / install the disc brake and 2) get a replacement spacer/stop.
I think you should be able to do that by contacting Florian as there’s likely stock and should be fair cheap plus easy to ship.
Without it you’re not really benefiting from the design of that 800 series hub.
Sadly me personally I’d simply not risk running an outboard brake - crank stop or no:
It feels like a way to wear out your hub’s internals before their time.
Still given you’re got it set up this way, getting the stop and using that is probably your fastest option to get it up and running semi-safely.
I feel bad for being the a bit doom laden here, but I’d always be slightly weary of a solution from a LBS - as I just feel they’re never going to know as much as uni-folk do regarding the dos and don’ts for these hubs.
I hope you get it sorted soon 
