TW,
One of those subjective situations that is hard to duplicate in a forum situation. However based on your scenario, I would be very loud about defining "my space;" I would go with the restroom idea you mention if available; I would defend the restroom as my safe space; if forced from an area with multiple escape routes to an area such as a corner, I would be prepared to use deadly force since the retreat option would have been removed; and above all, my firearm, or other weapon, would be deployed but hidden (note many Best Defense lessons on gun or knife in hand but in armpit or under garment.
I do not see what took place in this business as automatically dangerous and deadly, but it is on the edge that it takes very little to turn deadly. I wouldn't want to deploy any tool that would ignite the powder keg, but I also would not want to be left without options if it turned bloody.
It is situations like this that remind us all that there is no perfect answer. It is totally subjective and subject to Monday morning quarterbacking. All we can do is study, practice, discuss and debate in places like this, and be alert.
One thing to keep in mind is that I play Walt Rauch's "be gristle" to its perfect level. I am 6'1", 300#, full beard, and a booming voice that is not only very distinct, but if it doesn't demand respect it at least demands attention. When I am on the street and someone "invades my space" I can clear a crowded sidewalk with my command to stop or back off. Not everyone can defend their space with their voice and stature like I can, but I can teach almost anyone how to use their "big boy (or girl) voice." Once I moved my way from Unconscious unaware, to conscious unaware, to conscious aware, and finally to unconscious aware, the best tool in my self defense arsenal is my ability to command through vocalizations and body language. Once again, easy for someone with my biologic makeup, but learnable by anyone.