I don't speak or read Russian myself, but I'm trying to find some genuine and natural-sounding Russian equivalents of a couple of English phrases.
The first is "keep your shirt on," a colloquial and slightly irritable way of telling someone "calm down" or "don't worry". I found a phrase on a couple of informational websites that seems close: "В ус не дуть". I understand it translates literally as "not blowing into one's mustache", and is meant to convey a sense of calm and ease, though it isn't clear if it is meant in the imperative sense (i.e., "not worried" vs "don't worry"), which is what I'm after.
The second is a term of endearment with a sarcastic inflection, such as "slick", "sparky" or "sunshine" (e.g., "when I want your opinion, I'll ask for it, sunshine"). Interestingly, I found a reference to a diminutive term "лучик", which apparently translates as "little ray [of sunshine]" and is typically meant affectionately. Practically any English term of endearment originally meant affectionately can be delivered with sarcasm, and I was hoping the same was true in Russian. Can anyone confirm this for "лучик", or suggest an equivalent term of endearment more often used sarcastically? Preferably one in the common parlance, of course.