Your idea inspires me to propose the following: "nawet nic nie mów" or "lepiej nic nie mów" or perhaps even "szkoda gadać". I believe both serve to emphasize the speaker's exasperation at the situation their interlocutor makes a comment on.Yes, I think it is good. Another one would be: Nie musisz mi mowic.
"Co ty nie powiesz" quite escaped me. Would you agree, however, that unlike the other ones, it implies irritation with not just the thing being discussed, but also irritation with (or even hostility towards) the person who brought the subject up?The Polish phrases you came up with, Jarek, are just fine. It seems you figured it out quite well on your own. Another way of expressing the idea in Polish might be: "Co ty nie powiesz?"
"Wiem coś na ten temat" is the phrase I would be most likely to use
do you think that coś o tym wiem is a good translation?…Yes, it certainly is. It's not a nice thing to say but I wouldn't go so far as to say it implies hostility. It sure does imply irritation, though. But then again it all depends on the tone of your voice - I can imagine using it in a light-hearted manner.