No need. Even if she makes no income, you will just file married filing jointly.

Yes, you should apply for an ITIN for your spouse even if she is a house wife. There are other benefits for your family if she has an ITIN which is related to future Comprehensive Immigration Reform. This is proof of her presence in this country for when you are ready to process any immigration application.

This number should not be used for employment. But it could be used for banking purposes.

In order to fill out your tax form and include your wife, you will need an identification number for her, even if she has no income. If she is unable to get a social security number, the ITIN is just as valid to the IRS.