alaek - Welcome, glad you're here!
Good questions, most of which you'll have to answer on your own.
I drank in my 20's like you did - then my 30's, 40's and part of my 50's.
Some people are heavy/binge drinkers and simply grow up and out of the bad habit. For most of here, we never grew up - so to speak.
Thinking you have a problem, coupled with blackouts - not intending to get really drunk etc can be a big warning sign. Stop for 90 days - drink nothing. See if you experience the obsession to drink during this time and cravings.
Either way - you will find that a life without alcohol will present you with a better quality of daily existence and open doors you never dreamed of......
Thanks for the post!
fly