the front derailur has two limit screws labeled l and h. you need to back out the h screw a bit.
for the rear brake, there may be a little screw running perpendicular to the brake pivot. if there is, try tightening that screw a bit. otherwise, I think you will need a new spring. (just to be sure - you say the brake arm just falls - towards the rim or away from it? - it is ok if the arm falls away from the rim - this is what is supposed to happen - you should only feel the spring when the arm get's close to the rim.)
these components are not the best, but i'm sure you already knew that. But it sounds like you have all of them working well, so I wouldn't worry too much about them. Basically, if something breaks or wears out, replace it with a better component.