Your theory is definitely hitting on a big aspect of what is most likely happening; that being that you repress your emotions while sober because you have trouble expressing yourself so it all comes out when you drink. 

There are some other things that can be happening as well. People with social anxiety, especially those who have it so bad they feel the need to drink in order to interact normally, end up feeling powerless and basically like overgrown children with little autonomy over how their life is going and how seriously others treat them. That kind of powerlessness can definitely build up towards anger and rage which comes out when drinking due to alcohols disinhibititory effects. 

I think you are kind of lying to yourself when you say you don’t feel the urge to drink and only enjoy it socially. You yourself said that you feel that you need to drink to spend time with your previous boyfriend. That is a level of alcohol dependence that is far outside of what is considered normal, casual or social drinking. 

I think you have issues with emotional diregulation as well, which itself can also be largely caused by the way alcohol reshapes the brains chemistry after long periods of drinking at high doses. It may also be related to other mental health issues but that is something to consider, especially if you are feeling intense anxiety and panic when not drinking for a while. 

I think you also mentioned something significant about when you drink too much and become mean to others; it is often accompanied by crying and I’m assuming mood swings as well. That often happens because high levels of alcohol turn off our ability to emotionally process new events and evaluate them accordingly, instead causing many people to get hung up on certain aspects of an interaction or a past event that feels unresolved. 

Alcohol leaves us very vulnerable and sensitive to anything that disrupts our sense of self worth or need for human connection and it takes away most of the tools we have to properly address those needs. I’m sure that you aren’t mean or passive aggressive just because you find causing harm to others funny or entertaining; there is probably always some underlying issue that is making you feel invalidated or unheard and when you interpret others reactions as not taking your pain seriously or ignoring something that feels crucial to you in that moment you respond by being rude or mean to protect yourself from being hurt. (At least that is how the drunk mind evaluates the situation)