I think this is a result of r/MaliciousCompliance. Some owner/manager told their staff to order these signs, when asked for what they want on them, owner/manager said "whatever is already there is fine" without looking at it.

Your parents sound as if they are low-key abusive towards you. Giving someone the silent treatment is abusive and controlling. I think you need to move out, if you haven't already, and consider limiting your interactions with your mother especially.

Also maybe just set up a lunch where your brother and grandmother can meet your bf.