Hey Ugh, that doesn't sound good man. I'm sorry to hear about how you're feeling and what happened at your job.
How did your interview at Wal-Mart go? I hope it went well, man. If you haven't done it yet - good luck!
This post may be tl;dr but I hope you take the time to read it:
I doubt your current employers will fire you. You sound like a very important and experienced employee, despite them giving you so much crap. If anything, use the rest of your week off wisely. Make sure your resume is all nice and up to date and start looking for other jobs. When you have this meeting with the manager, well... I agree with everyone here, I think you should apologize. Don't just say "I'm sorry" but try and explain that you got frustrated, lost your composure and that lately you've been feeling stressed out. If they ask why, you could try and explain what's been bothering you at work. I know it sounds hard and I know it's easier said than done but just think about it. Like I said, use this time and this week off wisely.
I remember you telling me you've got crazy hours, like working nights and stuff... I think finding a day job would be good for you. Means you could get a regular sleeping pattern going and you could begin a "normal" social life. When I say "normal" I mean in terms of times and whatnot, since most people work during the day and have their afternoons and evenings free. You could also get into social activities and stuff during the afternoon/evening too.
I really think getting another job, preferably a day job would help you out a fair bit man. It sounds like you need a change.
People are probably going to roll their eyes at this but I'm being serious. Off topic from the job but keeping on topic of depression (and I mean this with no disrespect), have you considered maybe taking up a sport or a martial art/self defence or a physical hobby of some sort? If you worked a day job, you could get into something like this as they're most commonly held during the afternoons/evening. Physical exercise is known to make us feel good and better about ourselves and can combat depression. It won't stop it over night but it can in a sense, treat it. I know time is the issue, but again if you had a day time job you might be able to give this a go. Find something that interests you, something you might enjoy and give it a go, you don't have to stick with it if you don't like it but it'll be good for a few reasons - you'll be exercising, lose weight, get healthy and you'll meet new people and make new friends.
This is gonna be biased of me but I would suggest taking up a martial art, because then you'll learn some groovy skills. Maybe dancing? That would be cool - I'm being serious too. I've always wanted to learn how to dance but honestly don't have time for it, or at least won't make time for it due to other commitments.
Depression is a nasty thing, a lot of us have been there. I know I've been there. At the very least, you're reaching out to others to at least try and talk about it and that's doing a lot better than most people already. That's a good step in the right direction.
And like madster111 said... Australia is pretty cool place.
Although it's expensive as hell to live where I am, and it's not even that fancy! -.-
