Why can't I change my name in minecraft?

Clicking the edit profile button and changing that name is not the real name.

To change your username:

• Log in to http://account.mojang.com.

• Click Change, next to your Minecraft name.

• Enter a new name and enter your password.

• Click the Change Name button to confirm.

Your username has been changed.

Now wait a couple minutes (up to 15) and logout and log back into the launcher again.

You are correct in that Minecraft does not accept the username -=maxdude2074=-. Minecraft usernames can only contain letters and numbers. Therefore, unless you have an alphanumerical replacement for -= and =-, I suggest not worrying about username changes at present, as there is a cooldown for name changes.