Hi Danniim
Well done on managing to get your supply up this far. It takes alot of dedication to relactate, or bring your supply back up. I have had issues with supply going up and down since DS was born, I even gave in and bought a tin of formula.
Recently one thing that has "amazingly" worked is activite. You can get it from your supermarket where the milo is. Its not expensive, I started off having a glass morning and night then only once daily and now not at all. After 2 days I had milk pouring out of me.
In regards to actual feeding, maybe try to express during the 10-2 break 1-2 times, and if your not up to much in the evenings, I would be expressing every hour until you go to bed, esp if he sleeps till 5ish. Generally 10 mins each side is enough.
I agree with Jennifer13, your BB's should produce enough milk to support the child, no matter how big they are.
Have you tried hand expressing? I find it easier, a little messier but not as much cleaning up, just make sure you have a cloth that you can wipe your hands on, and change hands and BB often until your not getting much out. Like everyone has said, its not about how much you get out be how long your stimulated for.