Norman explained it very well. Some other examples: that's a lie if I've ever heard one= that is clearly a lie. It clearly seems like a lie to me. If I am at all able to distinguish truth from lies, that sentence is a lie. If any sentence that I have identified in the past as a lie was correctly identified as a lie, then this one is also a lie. He's a smart man if I've ever seen one= he is smarter than any other man I've ever seen. If any of the people that I've called smart in the past are actually smart, then he must also be smart.

The expression "if I ever did see one" emphasizes what comes before. In this case, "If I ever saw a dream to comfort and protect this drunkard (that I am) she is that dream, that superlative perfection who will stand up for her man no matter what state of intoxication he is in.

I believe it is more like your #2. However, it is more like she is a dream come true for a "drunkard" because she protects him