Ah, I think the line about "When figuring out the Range on Push, use the power’s level" is referring to this line from Range on page 40:
The distance your power can affect (at Mid range and higher) is based on the power’s damage multiplier (if any) or its level (if no damage multiplier).
Mid range and higher are listed as multipliers, not flat ranges. So a mid range power has a range of x5 times either the DM (if it does damage) or rank (if it doesn't do damage). For Push, since it doesn't really do damage, it is saying use its rank when figuring out range.
So that said, let's see what happens here...
Bashman clarified that the stat you use for determining damage (for both Special Attack and Push) depends a bit on the concept. If the character is using his might to slam the ground or the target then it should be Brawn. Otherwise, the default is Mind for area attacks.
I don't know Hammer's stats, so for an example let's say he has Brawn 5 and Mind 3, plus Push 5 defined as +3 DM and 2 points for area so a Medium Burst.
If he's slamming the ground (or doing the uber-clap that Superman does sometimes), then it would use his Brawn as the base, for a total DM of 5+3=x8. If he's using some kind of wind control due to his spinning or something, then it would be based on Mind, so the total DM would be 3+3=x6. And since it is Push, the actual knockback distance (in feet) would be twice that (so x16 or x12!).
If you have a high base stat, you don't need much Push to get a lot of knockback. That's why in the archetypes, the Behemoth for example only takes Push 2 and assigns both ranks to buy his Area, so he has +0 DM from the Push power. Since the base is his Brawn 5, he's still getting a x5 DM (which is doubled for x10 knockback).
It sounds like you're looking for a high-end Push, which based on the archetypes means you're aiming for at least a x10 knock-back. That means you want a minimum DM of x5 (before the doubling). You need to decide which stat your type of Push is based on, and then add enough ranks of Push allocated as bonus to DM to bring that up to 5 (if it isn't already). Then buy the amount of area you want.
I apologize, I'm not sure I'm explaining this well. Did that help at all?