I don't know when you'll be back to check in but I'll say that I've never heard of doing a blood glucose test at home on any rodents. I know some chinchillas can be clinically diabetic but it usually doesn't manifest because the chinchilla's normal diet has very little sugar in it.
If you're feeding treats or have a poor quality diet, which is very common and many off the shelf diets labelled for chinchillas are, to put it bluntly, poisonous to them.
I don't want you to feel bad if you've been misinformed on diet though but both diabetes and phosphorus imbalance are likely caused by improper diet. Unfortunately because your chinchilla has a history of malocclusion it probably hasn't been eating right and many owners will give their pets treats and things they'll take, which only makes things worse.
I also know that most chinchillas that are having problems are given syringe fed diets. The most popular is Oxbow Critical Care which should have the correct Phosphorus to Calcium ratio. Ca looks okay.
Low ALKP is consistent with malnutrition as well. Low Phosphorus could be from vitamin D deficiency or not consuming enough food. My best guess at this point is your chinchilla is having serious digestive troubles.
How is fecal output and weight? Are you syringe feeding?