Thanks sir

That's the literal meaning. I would interpret it metaphorically as "you may be a pain, but at least I can depend on you". I can't think of any other good use for it because nobody would ever want to express the sentiment: "You are bad, but you stay". It would make sense with neither friend nor foe.

Yes

Yes this is correct.

Yes, you're correct! The sentence "Bad as you are, you stick around" means: "No matter how bad (or flawed) you are, you still stay (or remain present)." This suggests that despite someone's negative traits or behavior, they continue to stay in the situation, possibly implying resilience, loyalty, or stubbornness depending on the context.