They did take deductions from my paycheck. If you were an independent contractor, you should have receive a form 1099-Misc. reflecting you payment. You, do not need to attach the 1099 to your return. So if you kept good records of your independent contractor income, AND I HOPE YOU DID, you should be able to complete the return. If you were an employee, and don't have the check stub year to date info I mentioned above, contact the IRS for further assistance with your former employer.
Answer is too long to do here.
Generally, IRA corrections must be made by the due date of the return for the year in which the mistake occured. You are PAST that time period. I am unsure about whether this is a deductible item. Unless you can show that the room is used exclusively for business purposes, I think you're out of luck. But I'll bet you could throw a heck of a party in that basement.