1) It's $125,000 for 2007.
2) Form TDF 90-22.1, available on the IRS website.
Can't answer your third q personally, as my husband and I are both the same citizen, domicile, and resident status. But part of your answer lies in what you are comfortable with. Some couples go ahead and have everything owned by one person to avoid the tax of one country or another. Other couples are very uncomfortable not owning everything 50/50, even if it means they will have higher taxes. Most couples I work with do something in between.