If your system is constantly loosing pressure over a short period of time then you have a leak, it could be anywhere, and very small. Or the pressure release valve on your boiler could be passing water, or possible the system expansion vessel pressure maybe low and the system does go above 3bar and release water when on, eitherway it should be diagnosed and solved.
Constantly introducing fresh water into you heating system will increase corrosion and lead to eventual boiler and system failure.
As regards topping up the boiler pressure your self, as long as you know where the filling loop is located and how to use it, then there is no issue doing this yourself, only do it when all the rads etc are completely cold, then increase the pressure to between 1 and 1.5 bar (if you go over then vent a radiator until you get between the values stated)
You radiator problem sounds like a circulation issue and would need further investigating
I am an asthmatic, I work most days in the cold, outside boilers, broken systems etc, but never found it effected me, actually the opposite, warm stuffy houses would drive it mad