I'm in a similar position, I'm an alcoholic and I also take pills that give me tolerance to GABA. even though I have N, there's a possibility that I'll be on the group of people that take over 24 hours to die from it instead of the usual 15-40 minutes on normal people.
phenobarbital is much weaker, but it can definitely kill you. in your case it depends on how long have you been taking alprazolam, this benzo is notoriously easy to get addicted to without you even realizing , I'd say that if you've been taking them for a short period of time (less than 2 months) then you could ask your psychiatrist to help you cut down the dose until you no longer need it daily, but be careful because this is really hard to achieve if you've been using it for longer periods of time.
yeah, GABA tolerance in general is extremely hard to regulate. many people find that it never truly goes away, and those who manage to lower it go through hell with withdrawals that can last for years. it's a common opinion on drug forums that benzos and alcohol have worse withdrawals than heroin.