You need to stop immediately... or as quickly as you reasonably can. Your usage at this level is potentially dangerous. While it does seem that there is a lot of variation in individual response to long term, high dose Phenibut, the original Russian literature does state that doses in excess of 7 grams or so can cause "kidney dysfunction". This probably explains the frequent urination and potentially other physical symptoms you are experiencing, but if you do not heed the warning signs you could be risking permanent damage to your kidneys - you may already have increased your lifetime susceptibility to chronic kidney disease or drug-induced injury.
I'm sorry to say it but you are just going to have to tough it out, and please forgive me for saying but honestly if you tried to be disciplined and still managed to get up to 9 grams within 10 months, I would hate to imagine what would have happened if you hadn't tried to be disciplined. Bluntly, you are going to need to try harder now. Phenibut withdrawals are overwhelmingly reported to be not nearly as bad as withdrawals from other GABAergics such as benzodiazepines and alcohol, and the risk of physical danger during withdrawal, ie, life threatening seizures, is lower (although it may not be nonexistent).
You might think I am being over-dramatic and potentially harsh to you here regarding the risks of not quitting but I am saying this in the hope that it gives you the kick you need to get out of the admittedly unfortunate situation you have got yourself into. Additionally, many people consider Phenibut to be physiologically almost entirely benign and while in low doses this may well be the case high doses are not well studied and may not be safe long term - if you value your kidneys, stop now.
While Gabapentin and Baclofen would no doubt help the withdrawals I would suggest that given your inability to control your use of Phenibut, switching to a psychologically "harder" GABAergic drug is probably not advisable. Some people report some success using racetams such as Piracetam or Fasoracetam during Phenibut withdrawals but in my own view the effect is likely to be mild. I would suggest that the best way to manage your withdrawal would be to plan a good week or so when you need to do very little, and then just accept you are gonna be pretty useless and cut off from the world during that time. On the other hand, physical exercise or other activities that can keep you out of your own head while you are feeling more prone to panic or anxiety will also help massively even if you don't feel up to it at first. If you genuinely can't control your use then measure out as much as you need to taper and then throw the rest of your Phenibut away, then just take a week to be kind to yourself and recover... again, you are (likely) not in any physical danger. Psychologically I don't know your history but if you have ever been diagnosed with any kind of anxiety disorder then you should probably seek counselling as soon as you can, and depending on the assessment of the mental health professional you see you may be prescribed something that would help your symptoms instead of self-medicating. I would also suggest that while "withdrawing" you reach out to any friends and/or family you can lean on. On the other hand if you have been using Phenibut purely recreationally and don't have any history of mental illness, while all of this advice remains applicable, with a little more self-discipline you should be well equipped to get yourself past this. Good luck!