How much do you think I am worth per hour? Here's my dilemma..?

I am only making $13 an hour at my job now. I create Invoices, Customer service, Dispatching, Payroll, Reception, Purchasing, Filing, and Accounts Payable. I need to make more money therefor I had an interview yesterday for this company that will pay me $15. Should I ask for $16 since I have experience of 6 years Administrative istant position. The person that interviewed me said that the work load is double than what I am use to. She said my qualifications are perfect. The job posting said $15- $17 an hour. I would love to make $16 how can I request that amount? I have my second interview tomorrow with the owner. I need advise please help. By the way..I finally left my cheating , beating ex, I got a spot for $500 a month. I am starting school next tues. So now my target is getting a new job that pays because now I have to pay $500 that I never had since my ex of 5 years took care of me. I am scared yet not discouraged to be out there on my own. I know GOD will take care of me.