Sounds like he's impatient at those times. Any way to feed him a little early during those fussy feedings? Before he's STARVING? :) Maybe every 3 hours during that part of the day. The fact that he's feeding normally during the night and first thing in the morning I wonder if the teething is really bothering him that much - maybe it hurts more at certain times of the day... You certainly pump more then I ever could, 4 oz. was my max. Hang in there, he's a strong willed little guy, and how you respond during these times will build up his expectation in other areas where he tests you. If you want to pump and bottle feed during the day, then go for it, otherwise I'd suggest trying to find ways to make breastfeeding happen when he's not so stressed out and impatient.
My daughter did this, but it was at 8 weeks old, two weeks after a weight loss crisis where she ended up 10 oz below her birth weight. We were put in a position of having to supplement and using the bottle made her reject the breast completely. Even though by 8 weeks she'd gained enough to be back on track, the trauma of the crisis kept me from being patient about continuing to breastfeed. She won and never breastfed again. I was devastated. If that ever happened again, I'd get help from a lactation consultant and keep that bottle far far away. However where I lived we didn't have anyone to help us and my husband was very worried and unsupported so I gave in. Now with my daughter she refused to breastfeed at ANY time of day, so its certainly different then what your son is doing. However the impatient aspect is definitely the same. She wanted it now and didn't want to deal with the hard work of breastfeeding. At that point I could only pump 3 oz first thing in the morning, the rest of the day I'd get 1-1.5 oz. so formula was the only option I had. It was a mess for me emotionally. So really I'm telling you all this because if breastfeeding is as important to you as it was to me, I'd suggest getting a lactation specialist to help you through this. If not, you can pump and bottle feed as long as that works for both of you.
Best wishes!