Hi Believer,
It's my setence, I know, and it sure looks silly without the entire conversation, doesn't it? I have been thinking about this. Another example of how a native speaker just "knows" it - and I'm sure one of the teachers of English as a second language can explain this better.
In a consturction I am NOUN (or he is NOUN) you need the article. But I am ADJECTIVE, you do not use one.
I am happy, he is rude. (adjectives)
I am generally a happy person I know. He is the rudest person I've ever met. (nouns)
You had used an example - something like "He is the rudest person I know" - rudest is an adjective describing person. There, you need the article as part of the noun phrase "the rudest person I know."
I am the happiest = I am the happiest that I know how to be. Isn't there a rule about articles before superlatives?
Try to do well vs. try to do THE BEST that you can? I am thinner than I was vs. I am THE MOST slender that I have ever been.
So we still come back to why you can leave out the "the" before happiest, which is a superlative. And this is where we need a language teacher. Is it simply idiomatic, or is there another reason? I just know that it "sounds" okay either way.
Regarding your second sentence, I would not have used the "and" - but I hope you will keep in mind that many of us write our explanations squeezed in between other activities in our day and don't spend the time in formal composition that we would put into more formal corresondence.