Angry that he felt it was appropriate to become so angry at me rather than using our safeword.

Yea, that's a big ass red flag that he's not ready for that.

There have been many times that he has been rougher than I may have liked at that second, but I have never complained or used our safeword yet

And honestly, this is a sign that YOU'RE not. Just because you haven't used the safeword or complained doesn't mean he's wrong to. It's inappropriate to compare what you're comfortable with against what he is. What you're comfortable with doesn't mean he's okay with it. So while he should have used his safeword instead of getting angry, he absolutely does not owe you no complaints or no use. You not using it is irrelevant to the issue at hand.

1, because I believe there is give and take in sex and have never truly been out of my depth, and 2, I believe in saving the safeword for a situation where I truly feel uncomfortable and want the action to stop.

If you're having issues with the safeword being too specific any only being to stop, fix them. Use TWO (or more) safewords. One can mean "you're approaching my limit, tread lightly" while the other means "stop right now." If you're in a situation where you're going to be at ALL, even the itty bitty tiniest bit, resentful if he stops the action, you need to stop doing any BDSM until you've fixed that.

What you've said does not solve the communication problem. It highlights it. You are using the word to communicate one thing, but expecting it to solve a different situation. (Stop vs slow down) If this is a sentiment you've expressed before, this could even explain his behavior. It could be he felt like stopping, but was afraid to use the stop word and grind it to a halt because you've previously expressed your issue with it being a full stop. Or if you've ever made similar statements about "Well I'VE never used it!" to him.

We can't tell you what to say to him. You need to talk to him. You need to do it without judgment. You're two people trying to solve a problem, working together. Not two people trying to fix the other persons issue. Closing off might be helpful for allowing you time to sort your emotions, but if you can you should tell him you need time to do that, and either way it should not be a permanent solution.

Please make sure to read the other posts here. As others have said you're playing in an emotionally vulnerable way, and I'm not entirely sure you're really ready for it.