VC - sorry to hear you are 'nervous' - it is not uncommon. In fact, take-off is the 'easier' manoeuvre as you are flying away from the ground. Now, that should really relax you for the landing
Q2: NORMAL procedure is to fly away and sort the 'problem' out. There is very little that requires an immediate 'turn-back' in a multi-engined aircraft. It is always best to sort things out slowly. I would guess most pilots, given no weather or terrain problems would settle for around 1000ft 'ish if they had to do it. That takes about 20-30 seconds to reach from lift-off depending on weight etc.
Q2: Airline specific. Different 'dings' etc for different things. Some 'ding' the crew after take-off to say 'ok to get up and start the service', some don't. Some cabin crew start the service then, some wait for the 'belts off' (some NEVER seem to
). Coming down again, the crew need a notice of time to landing. 10,000ft approximates to 10 minutes. Again, airline specific.
Q3: See Q2. In my experience, 1 'ding' for 'inter-cabin' chat, 2 for flight deck, some airlines use 3 to ensure crew are seated for take-off. More than that probably means very grumpy Captain
. I'm sure you'll get a load of other answers too!