You state that you know you can't cure him, but you also feel that being with you helps him reduce his drinking. You believe that you reduce his loneliness and depression. In the short term that may be true.
One of the realities of alcoholism is that it is a progressive disease. It doesn't get better, it only get's worse. Back in the days before AA, (and now there are other options), the prognosis for alcoholics was madness and death. It was a pretty bleak outcome. You rightly recognize that the path he is on is doomed to failure, although I'd challenge your analysis of why it's doomed. It's not doomed because he can't afford the help he needs. Rather, he can't afford the help he needs because he is an alcoholic. He drinks away his income, he makes poor decisions, he can't hold a job or save money. That's not a judgement, that's just a fact.
When we understand that "three C's", that we didn't cause the alcoholic to drink, we can't control their drinking and that we can't cure the alcoholic, it frees up a lot of misplaced energy and effort. It lets us focus on the one thing in life we can control: ourselves. We can work on setting boundaries, (and not caving). We can learn that "No" is a complete sentence and that arguing with an alcoholic is an exercise in irrationality (and doomed to failure). And maybe: "We will love others without losing ourselves, and will learn to accept love in return."
I learned about the three C's, and so much more, by attending Al-Anon meetings. I highly recommend it to anyone living with an alcoholic, particularly an active alcoholic. In that program, we're counseled to offer the alcoholic encouragement and support...but in a way that doesn't require us to sacrifice our own serenity and happiness.
I hope you find peace.