First off I'm very sorry to hear about the grief you're experiencing coming to terms with your father's deficits from drinking for so long. Can I ask when he is with other people what ends up happening what is his deficit in terms of interacting with people instead of the countryside and his dogs?
I'm going to tell you something that is funny. I used to believe my alcoholic ex-boyfriend that he just couldn't learn English and he just couldn't learn how to properly read or write in his own language because of an injury he experienced when he was younger. Me being codependent I didn't see anything wrong with this and I found it endearing actually and I ended up picking up a lot of the slack when it came to documentation. There were so many things that ended up having to help him out with not just because he didn't speak English but figuring out how to do most things with all on me regardless of the language.
For the year he pursued me he could barely remember my name and kept on changing it to other names that were similar to mine. I attributed it to his head injury and to him being a happy-go-lucky guy. The sad part is I understand now it was his alcoholism destroying his short-term memory. He was unable to learn English because of that as well and yes while his upbringing as a poor kid in Mexico did affect his ability to read and write the reason why he couldn't do it now was because of his alcoholism. It makes me wonder how much of an adult they are and how much of the endearingness how to do with nurturing someone who is functionally a child. The saddest part is it's not a choice or a personality Quirk or just inner work that hasn't been done it has to do with their brain chemistry is being degraded over time there's no coming back from it.
alcoholism and Other Drug addictions are self-destructive so it's not a surprise that the mine degrades over time but it is a shock for me to think about how in denial and how attractive to be quite honest it was at the time. I say attractive because I think it made me feel needed and allowed me to I feel like we had this deep connection