Because you are married, you cannot be treated as single. You can file a joint return, or you can opt to file as “married filing separately.” However, if spouses live apart and meet certain tests, one may qualify to file as head of household instead of married filing separately. To do this, you must have a qualifying person live with you (or a dependent parent even if not living with you); a spouse is not a qualifying person.
Depreciable property used in a trade or business and held for more than a year. All Section 1231 gains and losses are netted; a net gain is treated as capital gain, a net loss as an ordinary loss.