Welcome

- you'll get lots of great help here, and some answers to your specific questions but as I'm here now I'll start. (opps, I see the ever vigilant Virgil has beat me to the post ha,ha.)
Two things: First, going through detox, then taking Naltrexone while abstaining is NOT TSM. The whole point is to begin to take Nal while drinking regardless of whether you cut back or not. Dr. Sinclair maintains that detox will occur naturally as the Nal aids in the cutting back. While you go through a forced detox your addiction cravings are driven UP not down, so naturally you will drink huge amounts again. Check out the book on Alcohol Depravation Effect.
Second, alcoholism is NOT dependent on the amount drunk. I'm one of those who drink very little, however I CANNOT STOP DRINKING THAT LITTLE BIT. Hence I consider myself an alcoholic. After one month on Nal I am seeing changes but still MUST have my little tipple every night. I panic at the thought of not drinking it. Your Mum, God bless her, might sing a different tune if she were deprived for some reason of what drinking she does - or she could be one of millions who just is not an alcoholic. Volume is irrelevant IMO.
From what you'll read here, and from what others in your same situation will tell you, very heavy drinkers may take much much longer to be "cured" on Nal. Please read the stories of people here especially in the weekly reports and you will see a variety of drinking volumes, and a variety of ups and downs towards the cure. Good luck.