If you wanna go the edgy route- you can try: "still breathing" , "another day, another dollar" On the "hows it going?" variant, you can try: "Its going..."

So far so good.

You can answer "what's going on" with "nothing special" or "nothing much" but not "how are you". I agree with Jazz and Dylan

Hi, Leszek. That's not quite right, but you could answer that question with "Nothing special is going on with me" and you would be perfectly understood. Dylan listed some common answers you could also say.

I don't think either of those would be something that is generally said when being asked "how are you?". I would say common answers are: I'm good, great, not too great, not too bad, fine. However, nothing special or even nothing much wouldn't be something a native speaker would say.