If you're sorry, show me.
Well, when I was told "Sorry Doesn't Fix Anything!" as a kid, I would sometimes respond with "What would fix it?" To which my dad would answer "I don't know." or "Nothing can."
Whenever you can fix a problem, you should, of course. Put your money where your mouth is and all that...
But in something like a violation of trust, there isn't any real easy way to fix it, especially if you never hear from the person you lied to again. You can't take it back. You can just work to show that you're more than that. The onus is on the violated person to accept it or deny it.
So the one time my stepdad told me he was sorry, I told him it was not OK and kept reminding of the mistake like he did with me. Payback is a bitch.
Becuase I'm not sure it can be said enough, know that a pro psychologist can probably help you more than an internet message board can, and you don't even need to be nutty to go to one, just generally unhappy and looking for a way to change. They're there to help, after all. And they'd probably be able to draw some good ideas from this stepdad stuff.
For my own milage, this seems to be going right in tandem with you not wanting to just drop it. You need to forgive him for saying that to you, too.