In fact, if you lift 5 tons, you should be straining and having a difficult time. No, you shouldn't suddenly develop new powers. Creative use of powers is encouraged of course, but not such that the nature/extent of the powers is altered in anyway.

In terms of actual combat, it is simplest to define the interactions and roles in terms of an Attacker and a Defender. (Though in practice the roles often end up combined.) The most important rule of combat, and in fact, roleplaying in this sort of system in general, is that You only control your own character, and your character must act within those specified limitations, rp'd accordingly. As such, in all poses, you may pose the beginning of an attack but never the outcome (unless given specific paged permission from the other player). You can pose what your character is attempting and intending to do, but not whether the attack is successful and you certainly can not dictate the end effects or how much damage results on the target. This applies to all players.