Tanyal - With regards to your giving question...
The IRS does not have a filing status "unmarried but living together" so unless they are giving as foundation or business, you would need to identify the donation as comming from one individual person (household) or the other. Possibly, if you have a letter from them on file directing you to split the donation evenly, you might legally be able to split the donation 50-50 to each household. But to be sure you are doing the correct thing, contact a your CPA and have them give you an official answer.
John Schneider
Forest Hill Church