I'm a CPO. The best I can do for you is give you the information that you need to digest. What you do after that is experience and intelligence.
Levels of threat:
Low - Insulting you; making rude gestures, raising their voice, being arrogant, grandstanding, show-boating. Keep in mind any and all of these can escalate if improperly handled.
Mid - Visibly angry, irate with political, social, or political context (we call these burst-veins), screaming, threatening physical harm or injury, disturbing their immediate environment (knocking something off a table) etc.
High - Pushing passed someone or something to get to you; any reaching in your direction, brandishing a weapon (improvised or otherwise), manhandling, shoving, threat of physical violence with a weapon.
Note: This is in no way a comprehensive listing.
Example: Drunk person being loud and obnoxious, this is a Low level threat. That threat escalates to Mid level if that person gets into your space, at which point you should be attempting to de-escalate while calculating evacuation. Any further increase in force or invasion into your space becomes a High level threat. At this point disengage and evacuate. If this is not possible in any way, do your utmost to defend yourself. If the situation is life threatening make do what you can, claw a DNA sample off them.
In order of priority:
1) Reason, diplomacy - Dialogue, humour (not always applicable), apologise even if you did nothing wrong.
1a) - Attempt to evacuate.
2) Talk them off the edge - There is no need to fight, there are cameras, there are witnesses, this isn't worth it etc.
2a) - Attempt to evacuate.
3) Firm up - You need to go now or the police will be notified; Notify police, door personnel, security, staff.
3a) - Attempt to evacuate.
4) Numbers are strength If by now you are still unable to remove yourself from the situation, use numbers on your side if possible. Numbers are a deterrent, even when not aggressive.
4a) - Attempt to evacuate.
5) Use applied physical force - At this point, training and defensive tactics are your only go-to. Get it done.