cam belt has a tensioner that will auto tension the belt. just do as the manual says and it will be fine.
as for the aux belts, just make a mental note of how tight they are now and do them the same when you refit.
jack under oil pan is easiest. i have never had issues getting the mount back on myself without any special tools, you should be fine.
there are many ways to get the pulley bolt undone, some put a breaker bar on, and crank the car over to undo it. however, if not done properly it can break things.
i tend to put the car in gear and get someone to put their foot on the brakes and i undo it. you can also use an impact gun to get it off.
removing the pulley is best with a tool, i made my own. if you use screwdriver you will chip the fuck out of it, 99% of them are like this from previous monkey mechanics.
if you are really, really lucky the last person who did the cambelt would have put some anti seize on before fitment, that way it will come off easy
you dont need to drain the oil.
axle stands for the rear can either be put on the rear jacking points on the sill or as you say, on the rear beam. just make sure they are underneath the bottom damper fixing points as this is the strongest part.