You can use a 1040 or a 1040A if you are filing Married Filing Separately.

If you are married, you can legally on file in two ways, Married Filing Joint and Married Filing Separate. Married Filing Separate excluded you from getting any tax credits and you only get half of the Standard Exemption. I have never seen a case where Married Filing Separately was better. Married Filing Separately also requires you to include your spouses social security number on your return. If you are married but legally separated for at least the last six months of the calendar year you can file as if you are not married. This means you can file as Single, Married Filing Separately, or Head of Household.

No. If you are Married Filing Separately, then you only can claim your personal exemption. Your wife's personal exemption only can be claimed by her if you're Married Filing Separately. Your spouse, whether filing jointly or separately, can't be considered your dependent.

No, you can file married filing jointly or you can file married filing separately

If you were married as of December 31, you file as either 'married filing separately' or 'married filing joint' for that year.