Just a word or two on the strength and amount of weight you lift issue.
How much weight you need to lift to achieve certain muscle gains is a fairly personal thing. Sure, as your strength develops with time the amount you are able to lift will also increase. But it is good to remember that you do not have to lift competitive power lifter weights to achieve your workout goals.
The guys and girls you see in the gym lifting what seem like huge weights are either on a short trip to injury-ville, or have been doing it for several years and have slowly worked up to it.
Correct form, and intensity, is much more critical than the number of plates hanging off the bar. Heavier weight will come with time.
Even then, how much you can lift is not completely reflective of your strength. Other things come into play as well, like fulcrums and muscle attachment points. I mean, if it were just down to training alone, everyone would be lifting the same weights and there would be no world records etc.
So listen to your body when you lift - a 50kg bench press done properly can be as effective for one person as a 100kg bench press is for another. It is all about what works for you, not trying to compete with the guy down the way. There be dragons!!
James.