Can I apply for US citizenship?

How long have YOU been physically present in the US? Have you been outside the US with your spouse for the past 11 months? If so, you may have caused your permanent residence status to be terminated due to abandonment as you are not supposed to be outside the US for more than 6 months at a time as a permanent resident. If you have not been outside the US for all that time, you will be eligible for naturalization once you have been a permanent resident for 3 years if you got your green card on the basis of marriage to a US citizen and if you have been physically present in the US for at least of that time. If you got your green card status through some other mean, you have to be a permanent resident for 5 years before you apply for citizenship.

Yes, you can apply for citizenship after 5 years of continuous residence with your permanent residence status.

You can always file N400 after 4 year 9 month of your permanent residency. If you want to file in 3 years based on your marriage with a US citizen, you must show that you have been living together in the past 3 years. The fact that he is outside of the US for 11 months may be an issue.

You can apply for naturalization 90 days before your 5 years of residency if you are not living with your citizen spouse. If you are living with your citizen spouse, you can apply when you have 3 years of residency.

Whether you are eligible for U.S. citizenship at this point in time may depend on your ability to demonstrate your marital union or validity of your marriage. This might be problematic if your husband lived abroad. You should consult with an experienced immigration attorney for an assessment of your case.

You must have 5 years of lawful permanent residency in order to apply where you and your spouse have not been living together the entire time.

There are many factors to look at, including your own physical presence in the US, whether you have paid taxes or have any criminal record issues, the legitimacy of your marriage (even if applying at the five year mark.) Your spouse being abroad does not preclude naturalization however you would want to document your relationship carefully. Seek a consult with a competent immigration attorney in your jurisdiction before proceeding.