There are two issues here from what I can see. The first is your family being in debt, the second your birthday.
With the birthday thing I totally know where you are coming from. Its my 18th on Saturday and it was supposed to be having a big party, until my mum confessed she didnt have the money for it. I'm not going to lie, it got me down. Not because I'm spoilt but because Ive always wanted to share my birthday celebrations with all my friends.
The thing is, you can also come to lots of compromises and things. You can arrange to go clubbing or even to the pub with your mates. If you invite everyone you know, you're sure to have a great night and get lots of free drinks bought for you.
If you go for a meal... your friends will probably end up paying for you anyway.
Now there is also the issue of your parents finances. Trust me, sudden loss of money (I know its happened to me), is very hard to deal with. Especially if your friends have this preconcieved idea that you are loaded. There are always corners you can cut, and you have to just try to be that little bit less materialistic. Just because people cant afford to buy you things, does not mean they dont love you or want to spoil you senseless. Just because you cannot afford things doesnt make you any less important than anyone else, or make you an object of pity.
Try to explain the situation to your friends again, once they understand Im sure things will clear themselves up a bit.
As for the job, get posting/handing out those CV's and Im sure you will have something in no time.
And okay Xmas and your birthday might not be full of huge presents this year, that doesnt mean you cant still have a good time. Sometimes even the most simple nights out or even in, turn out to be the ones you remember.