I am in a heavily unionised job. Our unions sorted the problems out back in March. Are you in a union? The GMB is for those not covered by others, or USDAW may take you if it's retail. If enough of you join, it tells the employer your strength of feeling and you have greater collective bargaining power.
In the short term though, you need to take this up with your employer. Call a meeting with them, and get as many staff as possible to attend.
Consider:
Why aree there o queuing systems? Barriers? Signage?
Why is there not a member of staff (or employ a security guard) at the door limiting numbers? Do they have a mask, gloves, visor, maybe even a plastic apron?
Ventilation?
Lockers for use at different locations? Antibacterial wipes to clean them before and after each use?
Hand sanitiser available for customer and staff use?
The not wearing face masks with customers is unsafe, I wear a face mask with my customers. They wear one too (illegal in my industry not to). Stuff sales, your safety is important.
Maybe either an advance or on the spot appointment system is needed. So, book an appointment online, or turn up and be issued a ticket with a time.
Nobody deserves to be abused at work. All of the problems you list has led to the verbal violence. Your employer is being very negligent in their duty of care.
Solidarity, and I hope you can get this resolved.