You need to work on your shifting if the car is dying when you let of the clutch quickly, compensate with more gas.
I normally cruise at around 2500-3500 RPM. Cruising at 2k or 4k RPM is okay, but I personally wouldn't do it for too long. Also, you can safely take it to just below redline when you accelerate (as long as the car is heated up the 180 mark) but don't cruise for long periods at a high or low RPM's if you want your engine to last.
The car will heat up in stop and go traffic. When you are driving air is getting pushed into the radiators and intakes, when you are sitting the air has to be sucked in, so the car will run hotter. If you want to see what I mean idle for twenty minutes and you will hear the fans come on. It is really nothing to worry about, unless you start getting past the third mark toward 250. It should stay around 180 or just above it.
