Re: 5 minute nursings and crying at the breast..
Weight gain and diaper output indicate that your baby is getting plenty of milk in those 5-10 minutes. Babies can get lots of milk in a very short amount of time with overactive letdown (and what you describe definitely sounds like OALD). My baby could get a full feeding in just a few minutes (I think he was a little bit older before he got to that point though).
The block feeding should help some by reducing supply and avoiding any possible foremilk/hindmilk imbalance that you might see as a result of an oversupply. You can also try nursing in a reclined position. That is what ultimately saved my nursing relationship. I would lean back on a few pillows, put my baby on my stomach or chest, and let him latch. It can take quite a bit of adjusting the positioning to find something that works for you. Nursing reclined helps with a lot of the fussing at the breast because gravity helps slow the flow of the milk. Some women remove their baby at letdown, let the milk spray into a towel, then relatch the baby. My son had no patience for that, but it has worked well for others.
Babies tend to be really gassy with OALD. Some of the fussing can be due to gas in addition to difficulty handling the fast flow. I had to give a tummy massage then bicycle my son's legs between every single feeding to work out the gas incrementally. I also gave a warm bath followed by more leg bicycling every evening.
Babies are able to better deal with the flow as they get bigger. I sprayed for 15 months, but my son was only bothered by it for the first few months. Stick with it and it will get better!
K. Sophia - Mama to my little lactivore, the amazing Mr. X (11/10).