Considering he is being overfed at day are, you could lose your supply. I would consider adding a pumping session before you go to bed to keep up. 18 ounces in 10 hours is a lot. Alot.
I would check out kellymom.com for bottle feeding tips and pump advice. It's the leasing source for up to date and proven breastfeeding advice.
Also, to keep my supply I would go into my sons room at night, before I went to sleep, and dream feed him.
BFing, CDing, all natural mama to three boys! Certified lactation Counselor