You won't end up addicted to the alcohol, since it acts on the GABAa receptors, and GHB effects the GABAb/GHB receptor, so there won't be any significant overlap. Also, you will not get addicted to alcohol over such a short period of time.
If the dopamine rebound really is that bad for you, then your plan for getting some GHB free sleep sounds good. You sure as hell don't want to be anxious during a job interview, so it probably would be best to just ride out the rebound with some alcohol. Also, one thing I found that helped was to make several strong pots of chamomile tea, it definitely kept me more even keel. And even if it doesn't do to much for you, it'll at least keep you hydrated from al the alcohol
I would suggest not taking the phenibut. While it will put you to sleep, and decrease your rebound symptoms and anxiety, it has a fairly long duration (half life of 5 hours) and a steep dose-response curve. Also, it acts specifically on the GABAb recptors, just like GHB, so using if you use phenibut then the "opiates to replace heroin" analogy would apply. Also, tolerance to phenibut builds fairly quickly, and daily dosing will lead to dependence very quickly. Phenibut withdrawal can be very debilitating, since given its long half-life its basically an extended variant of GHB withdrawal. I've seen reports of people who ended up addicted to phenibut while trying to kick G, so it's probably not worth the risk.
Also, I can sympathize with becoming dependent on stuff at really bad times, and then having to do something like this. Hope it works out!