Hello!
In my personal opinion, I do not think you are wrong for not wanting to buy alcohol for him. He has admitted to having a problem already so you are smart not to enable him. Also, stress is not a reason to drink. In fact there is no good reason to drink...period. There is NOTHING good that can come from drinking alcohol. He is going to get mad at you, so be prepared for that. He will probably make you feel like you are a terrible person for not wanting to "help" him. You have to ask yourself what is important to you. Do you want to just hand him the poison so he can continue harming himself and pretend that the alcohol is somehow helping him, or do you want to truly help him by choosing not to enable him to drink? The reality is that alcoholism is a path to death and you will basically be helping him down that path if you agree to buy alcohol for him. Don't accept that his stress or pain is a valid reason for him to be able to drink. The truth is that an alcoholic will always find a "good" reason to drink no matter what the situation is. Believe me I know from much experience. I'm sad, so I'll have a drink...I'm happy, so I'll have a drink...I'm bored, so I'll have a drink...I can't sleep, so I'll have a drink...I'm stressed, so I'll have a drink...It's raining outside, so I'll have a drink. (basically anything and everything is a good reason to drink in the alcoholic mind).
If he cannot physically go out and get his own alcohol, and you also choose not to bring it to him, he will most likely experience withdrawal symptoms. He will be irritable and anxious in the best case scenario. However withdrawal can also be dangerous and include seizures or other conditions. So if you do in fact decide to not give him any access to alcohol, it's important that you monitor him or even tell his doctor that he is an alcoholic and may be going through withdrawals soon. It is obviously totally up to you, but if you are looking for validation that you are not being a bad person by refusing to bring him alcohol, here it is. I can't imagine that any recovering alcoholic would tell you to give it to him. Just be careful that he has medical supervision and understand that withdrawal is not easy.