Here my insights about おう and め 
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I’ll just answer by experience and exposure to the language, as far as i have heard, its kind of like a “yes” or “afirmation” word. The first person says じゃあな (like see you later) and so his friend answer おうまたな (like, yeah! see ya!).
I just felt a little bad answering you from my guess so i gloogled a little bit just to make sure i’m not saying to you something wrong, and found this that supports it:
おう、は、ここでは、多分「はい」です。Boys often use it instead of はい when they talk with their friends.
When you don’t know what to say, you can’t say words clearly, and say like this “ah-…y, yes”
What is the meaning of "お、おう"? - Question about Japanese | HiNative
I didn’t know that is only used for boys, but makes sense. I hear it a lot when i see haikyuu
As for this:
I think you have that right, everytime I hear め at the end of a sentence its for giving that entonation of cursing to what he is saying. In my experience learning asian languages, they usually have this syllables or particles (not sure wich name is appropiate) at the end of sentences that they don’t actually mean something as rephered to a word but they are like keys to give some mood, emotionallity or intention to what they are saying, め seems to be used when you are upset about something.
I guess this resource is something new we have to input in our way of thinking and learning japanese since we dont have that in western languages like spanish, english, etc (as far as I have seen).
Edit: more backup for my insights:
「め」 is a suffix of contempt when attached to a noun or another person’s name.
「この犬いぬめ！」= “You stupid dog!”
「許ゆるせん、田中たなかめ！」= “Will never forgive Tanaka the bastard!”
Translation is an art. You could use whatever word you feel appropriate for the context that expresses contempt, scorn, disdain, etc.
Please note, however, that it becomes a suffix of humility when attached to the first-person pronoun 「わたくし/あたくし」. This usage is much more often seen in fiction than in real life.
「私わたくしめにお任まかせくだされ。」= “Please leave it to the humble me!” You will hear subordinates say that to their bosses in period dramas.
We do not say 「ぼくめ」 or 「オレめ」 because those are far from humble. Even 「わたしめ」 without the 「く」 would be quite rare.
From here
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woah, i just learned how to use this tool, feels good