"- Misc (weddings, gifts, family occasions, etc) 100"
Moondance,
I think you may have hit on the critical point. If you ONLY buy the minimum amount of food, ONLY use the minimum amount of electricity, ONLY socialise with the minimum amount of friends, etc you may be able to live on 900pm (unfortunately the OP doesn't have 900pm - that was the figure metioned my momomo).
What you won't be able to afford is those "Misc" items. Now it's true that you can get by without these. But it's also true that you can survive without toilet paper. It's just that going without either is guaranteed to make your life less enjoyable.
OP, I applaud your determination - there's nothing wrong with making a stab at budgeting. But do yourself a favour : Set yourself a definite financial target, say 4 or 5 months from now, and if you find that you are slipping below that financial waterline, then you need to make changes. You may not want to take in a lodger, but at that stage you'll have tried the alternative. Agree now what those drop-dead figures are, and write them down where you can see them every day. It's very easy in four or five months to start convincing yourself that it's okay to move the goalposts. Don't.
At the moment your situation is serious but not critical. But for your own sake, don't be back here in two years time, 40k in debt and in real desperation...