I'd encourage you to take a step back and take an impartial look at the situation. You seem very frustrated and that'll hinder your ability to see the best way forwards until you can manage to put it aside.
It's very common for bosses to push more work than can be done in a work week onto 1 person. I recommend you establish a clear boundary along the lines of "Hey boss, my weekly workload is currently much higher than can be achieved in a work week. If we continue as we are now, a good chunk of this isn't going to get done. Which work items would you like me to prioriritize, and which ones are being shelved?'.
You have the time estimates you've provided to back your case up. Just list out all of your projects, put the total time estimate next to each one, then put the deadline next to that. Block it out into work-weeks, and see which projects you could meet by their deadlines, and which ones are beyond saving.
EMAIL this to your boss. Remain impartial. Don't threaten. Draw everything to the 'what's best for the business and clients' perspective.
As others have said, a few hours of overtime in a work week is reasonable if you're after a promotion or the company is in a crunch period. This goes hand-in-hand with being allowed to head home a bit early if you're in a quiet period. Tit-for-tat.
Determine how much overtime you would actually be willing to work if you were being paid for it (maybe 5 hours a week? Maybe 10?). If the subject of overtime is discussed, you can give this as a concession to your boss, while still retaining a limit that you're comfortable with. You should absolutely be paid for this, but in return it's something you absolutely have to agree ahead of time with your manager. In writing.
If all of this genuinely does fall on deaf ears and everything stays screwed after a few weeks, then you have your correspondance in email with a clear trail showing that you tried to resolve the situation and that your boss didn't respond. If you reach this point you can leave your position without looking immature or unprofessional. If you leave before going through the steps above, it would look like an inability on your part to properly handle the situation, than a reflection on your boss.
tl;dr take a step back and deal with the whole thing impartially.