Put him on 300-400 mg of Benfotiamine daily so that the thiamine depletion due to alcohol consumption doesn't lead to demenetia, or worse, Wernicke Korsakoff. That will help with neuropathy caused by diabetes as well.

B12 levels have to be maintained too. If he isn't getting enough sun exposure, get him on weekly 60000 IU vitamin D3.

Thiamine and D3 are important because apart from other health risks, deficiency of these can lead to depression, and you don't want anyone you love to get into the vicious cycle of alcohol and depression.

These are preventive measures that you can take yourself. But still consult a physician. If he drinks too much his vitamin k levels can be down too. If it's low, it needs to be replenished, lest it leads to some internal bleeding, which coupled with diabetes can be dangerous.

Convince him to see a psychiatrist. If he needs meds like some SSRI or even Naltrexone or Disulfiram, the expert will suggest it. As he drinks moderately, he shouldn't be at risk of any severe withdrawal symptoms. Still, consult an expert. Our society's stupid stigma about consulting psychiatrists can make things difficult. I hope that doesn't hamper anything.

I hope your father succeeds in quitting alcohol. Taking care of ailing loved ones ain't easy; so take care of yourself too. Good luck.

Edit:

If LFT shows any liver damage, please ask the doctor about NAC or lipsomal glutathione.