I love your post becuase I can totally relate. I think i saw no issue with how your handled matters up untill you said F it and had a drink. I think there in lies the issue. Get up from the table walk around the resturant if anyone asks say i'd rather not share my frustrations at this time and I'd just like to get some air and calm down. As important as the evening was to you the rest at the table clearly didnt realize that and how where they to know you had a surprise in your pocket?
Its a tough one being married as many years as you have I dont have to tell you. But sometimes you have to be firm no I'd really like it to just be us etc... Or you comprimise ok we will do dinner with them too but on another night etc...
Sitting there like an a-bomb stinks. It gets better tho. I still have my moments myself as much as everyone likes to make it out like its /me/ with the problem and sure sometimes it is. Its also just life. we are going to face circumstances that drive us nuts. The best we can do is try to avoid these situations and try to find ways to cope with these situations when we cannot avoid them.