Brooklyn, the goal is to get a defined amount of calcium into your baby throughout the day so that the calcium level stays up. The amount of calcium in each dose isn't large so have you considered using a syringe to 'blast' the calcium into his mouth in a small amount of water. If he won't take it willingly you might have to resort to force.
I doubt the MBD is severe in 9 days. I don't think the bones could have eroded to the degree that long term MBD sufferers experience.
Of course, it is true that the pine nuts with a calcium: phosphate ratio of 1:36 is just about the worst food he could have consumed.
I think this is more a case of a classic 'metabolic syndrome' where the calcium levels dropped so low that you are seeing the classic signs of MBD. Hopefully this can be normalized in a much shorter time frame than full blown MBD.
As far as the diet, you will just have to hold the line. Now that he has tasted pine nuts, he will resist the good stuff but I'm sure you can enforce the 'tough love' that will inevitably be needed.