being sober >>>> being an alcoholic. some people just can't handle it and have to go all out numerous nights of the week, and that's no way to live, regardless of your strength/size.
but yeah, you've probably just got great genetics, and your body will use any calories it gets efficiently, so when you stopped drinking and eating healthier, you cut back on calories. just replace it with good, high calorie foods. luckily for you it sounds like you could eat just about whatever, whenever and your body will use it efficiently.
on a side note... when i'm hungover the LAST thing i want to do is workout, so i don't think i ever have.... although my friends dad used to do powerlifting in college and said his strongest lifts were the day after drinking... not sure how that works for everyone since alcohol is full of pretty useless calories and the notions of it being loaded with carbs is GREATLY exaggerated. i used to think all the calories in even light beer came from carbs... until i looked and say that 1 light beer has like 1% of your DV of carbs