I'm with you on this. I also was diagnosed with Social Anxiety and I think dinner situations are the worst. I know where you're coming from. It feels as if there is a beam of spotlight shining down on you with every single action, move, comments, or even beathing pattern you change, it seems that everyone notices. As you mentioned initiating in conversation and joking... Friends and strangers and even family find me as a very humorous and joking kind of a guy, and I'm good at it. But little do they know, I do it as a deflection of my insecurity in the situations. I get nervous, I notice that my breathing becomes more focused and uneasy and maybe even start to sweat.
This seems to be a burden, that you are internally focusing on your actions when everyone around you seems to be carrying on with comfortable atmosphere. You're not alone. Sounds like you are taking great steps to lightening this type of anxiety with breathing and meditation. I have yet to try meditation. Try to convince yourself that what you think people are noticing probably isn't real, most often they are not focused in on these types of things. Sometimes it is hard to jump into conversation and a lot of people take it as an offense if you don't, but just simple agreeing words can get you involved in the conversation and chime in on topics you feel most comfortable about. Even bring up a topic of your own. This is difficult at first because you feel as if you are giving a speech to 100 people and you wrote it the night before.
More often than not, even just about all the time, You're really not giving off those signs that you have anxiety, so in situations like that... just dress the part and keep cool. try not to think so much into it. It's easier said than done girlie, I'm with you on that.