Go out on the market. Update your resume, try to get an offer. Be ready to accept it. Negotiate with your manager and show them empirical evidence you're worth more.
The reason you have to be willing to accept the other offer is that the moment you approach your manager with it, they might decide to replace you rather than promote you. But counterintuitively, your willingness to accept the other offer will work in your favor and is more likely to get you promoted than replaced.
Do not under any circumstances assume that loyalty to your job will be rewarded in any way. The fact that your manager was willing to let you work 70 hour weeks for a year is evidence you were being taken advantage of. That's life, though. The way to win is to play the game.
(There are situations where letting an employee work 50+ hour weeks is justifiable, e.g. if the employee goes into it with eyes wide open and without any implicit promises of future promotion or future compensation increases. Quarterly reviews with salary increases would also take it out of the "being taken advantage of" category.)
As a final note, it's very common for employees to force themselves to work crazy hours without any encouragement from management. It's not necessarily management's job to stop you from doing that, though a good manager will. I did this to myself my first couple of jobs, and had only myself to blame. I'm not saying you necessarily were doing that, but it's such a common story for someone to come into the industry with something to prove and convince themselves to dedicate their life to their job to the exclusion of all else.
Go home each day after putting in 8 hours. The door's right there. If you work harder than that, you should feel like you're getting an excellent deal out of it. And no, promoting you doesn't automatically count as an excellent deal. You should still probably work 8 hours outside of very special situations.
EDIT: If you're feeling upset that you got taken advantage of, don't sweat it. A year isn't such a big deal in the scheme of things. You're far more equipped now for your upcoming years than one year ago, for example.