You're being a bit harsh on him - what if his uncle really did die? And it's just a birthday, there's no need to wish death on him, you know? - how do you know he wasn't gonna make it up to you later? And anyway it's not really the birthday you're angry about is it? - it's just a trigger. You simply don't get this angry over forgetting a birthday - you're angry because he doesn't seem to care about you, and forgetting your 18th is an indicator of that - that's why you're mad. The b'day thing is just an excuse.
You two need to sit down and talk - if you feel left out, talk to him. It's not gonna work if you two don't communicate. Apologise to him - he's wrong in forgetting your b'day (I wouldn't be very happy either if it were me) - but you're wrong too - calling him names etc - why would you wanna hurt someone you care/cared about?
And the bottomline is, if he really doesn't care about you anymore - why are you hanging around? You're only gonna get hurt. Talk to him, and if he won't change and listen, then maybe you should consider calling it quits - it's unhealthy to be the way you two are atm.