I know the feeling, the obsessing over the past, the anger, and the search for meaning. I also know how it feels to "fake it" to try to seem "normal", and I know how hard and damaging that is… it can't last forever, and it's really draining.
Do you have any hobbies that you could channel your angry energy into? Lately I go for really long walks—getting sweaty helps me feel like I'm doing something that makes me feel intensely worn out, and it gets out a lot of the anger. A lot of people do arty things or exercise to feel better, but maybe even something like cooking or writing about what makes you mad (or something else entirely) could help. It can get your mind off it, make you feel busy, make you feel productive.
Also maybe there is someone you can talk to about how you're really feeling. Maybe a relative or counselor or therapist. A lot of times your family is the best thing, because they really know you, and they care a lot more than you probably think. Just talk to someone you trust. It may help you answer some of the questions you have…
I don't think anyone can tell you whether there is a purpose for existing, but I do think family and friends are the first thing most people think of. I also think just getting through each day and making some kind of schedule for yourself, some sort of structure can really help. Even if it's just waking up, making coffee, going to work, etc, you can try to do things that make you feel good and positive and go from there. Go see a movie or take long shower or see a friend. I know even when I don't have a job and I feel lost and hopeless, making a schedule for myself is important and makes me feel better. It's like baby steps… and the happier you get the more it will become clear what's important to you, what makes you really happy.
Hope you feel better.