RaindropDZ

It is usually better to file Married Filing Jointly but right now you can file Married Filing Separately and once your spouse comes to the U.S. and gets an SSN you can file an amended return to change your filing status to Married Filing Jointly.

You are correct. You can file as Married Filing Separately just by listing your spouse's name and entering NRA where you are supposed to put your spouse's SSN. It doesn't matter whether your spouse earned any income in his/her native country. A nonresident alien is only required to file a U.S. tax return if they have income that is considered earned in the U.S.

No, if you file MFS you can do so even if your spouse does not have a SSN or ITIN. However, you won't be able to take an exemption for your spouse, but you can still file the return by writing the spouse's name along with NRA.
If you elect to file MFJ you can file the W7 concurrently with the 1040, but you must then include your spouse's income (worldwide income of both spouses must be reported). This usually isn't an issue unless foreign income exceeds certain thresholds.