If you file from abroad, you get an automatic extension until June 15th. I just write 'tax payer abroad' on the top of my form (per advice from the IRS at the embassy in London).
As far as the interest on your US account goes, you file this on Schedule B (you can download all the forms/instructions from the IRS website). You should have received a 1099 from your bank to include with your taxes. You will not end up owing any tax on this money, as it is well below the standard deduction ($5,450 for married filing separately for 2008).
You should have a W-2 from your part-time job, and you should declare this on your 1040.
Have you been working in the UK? You will need to report this as well. You don't say how long you have been living here, so not sure if you are eligible to file the Foreign Earned Income exclusion.
You will also need to file form TD F90-22.1 if you have had more than $10,000 in a foreign account(s) at any point during 2008, including joint accounts. My understanding is that you use the exchange rate from Dec. 31, 2008.
Sorry, I can't answer your questions about the money sent from your husband.