Personal Taxes

If you lived apart from your spouse and your child lived with you for most of the year, you may qualify as unmarried head of household if the following criteria are met.
Your spouse was not a member of your household during the last 6 months of the year.
You provided over half the cost of keeping up the household. You maintain your home as the principal place of abode for your child, stepchild or adopted child for more than half of the year. You are entitled to claim the child as a dependent.
Speak to your local CPA if you still have a question about your filing status on your tax return.

If you are unmarried at the end of the year, you may be able to file as a head of household or widower if you pay for more than 50% of the household costs for the child or relative that lives with you. You may file as a widow(er) if you became a widow(er) in the 2 prior tax years, and in the current tax year you paid more than 50% of the household costs for you and the dependent child. The tax rates for widow(er) and head of household are more favorable than filing as a single.

For the current year, If your filing status is head of household and you are under 65 then your gross income must be at least $12,850 ($12,500 in 2012). If you are 65 or older then your gross income must be at least $14,350 ($13,950 in 2012). Gross income does not include Social Security benefits.

No. To use the Head of Household filing status, you must have paid over half the cost of keeping up a home for you and a child or other qualifying person for over half the year.

AMT stands for Alternative Minimum Tax. The Alternative Minimum Tax was developed in 1969 to make sure that wealthy taxpayers didn't escape paying income taxes. The tax was meant to target high-income taxpayers who may have many deductions and can sometimes avoid paying any income taxes at all.
To make sure that all taxpayers with substantial income are not able to avoid paying tax, the law limits the benefit a taxpayer can receive from favorable treatment of certain deductions and preferences.
The Alternative Minimum tax is computed on IRS Form 6251.
If the Alternative Minimum tax calculation results in a higher tax then the Regular income tax, then the difference is added to the Regular tax computation.

If the filing status you are using for filing your individual income tax return is "married filing separately", and your spouse itemizes his or her deductions, then you must use your itemized deductions even if your standard deduction exceeds your itemized deductions.

Some spouses have had problems with the IRS in the past and still owe the IRS taxes. When you file a joint return, you and your spouse are both equally responsible for the taxes owed on that return. Any refund you might have been entitled to could be used to pay your spouses existing liability with the IRS or the state. Lastly, some people do not want their spouse to be aware of all of their financial involvement.

If you are filing as married filing separately, both persons must file using either the standard or itemized deduction amounts. One spouse cannot use the standard deduction and the other use the itemized deduction amount.

If you are Filing as Married filing separately, you must have lived apart from your spouse for the last 6 months of the year to take advantage of the dependent care, earned income, elderly credits and the $25,000 rental loss allowance.
Also Social Security will be 85% taxable.
Speak to your local CPA about the tax strategy of using married filing jointly or married filing separately.