You could still have a nice body or be in good shape but not be healthy. Also just because you are sick doesn’t mean you aren’t healthy. To know if you’re healthy you need to know if your body is working correctly and make sure everything is at the regular or healthy level. Not high or low.
20% is absorbed in the stomach while 80% is absorbed in the small intestine. Alcohol its self doesnt hurt your stomach lining but it does increase your stomach acid that will eat away your stomach lining.