I just had another conversation with someone about this topic and I wanted to add this because it came up.
You seem to be confused about whether "Allah" is a proper noun or a generic. Like the word "God" in English it is both.
I think it is a confusing concept, but one way to think of it is one word with two meanings. God can mean "the one monotheistic god" or it can mean "a deity." But when translating a word to another language, it's not true that every meaning gets translated the same way. As a concrete example, the word "set" has tons of English definitions. One translation of "set" to German is "Satz." That encompasses several of the same definitions as "set" including "a collection of things" and "a series of tennis games."
But another definition of "set" in English is equipment, like a TV set. In German that gets translated as "Gerat."
So even if it's true that one form of Allah (the generic form) should be translated as God, that doesn't hold that all meanings of Allah should be translated as God.