Which supplements do we need for VLCD?

Hi @Rabdos I'm surprised that you've not had responses before this.
I have not done VLCD since I'm/was TOFI or a slim Type 2 - so didn't need/want to lose a lot of weight.
I can't answer many of your questions, but I hope I can help a bit:

First of all I hope you are aware that it is dangerous to do VLCD for too long. Most programs of it only last for 8 to 2 weeks.

1). Protein: this number of grams per kilo is not based on your current weight, since you are actively trying to lose weight, it should be bases upon your target weight.
2. Fibre: there are debates about whether we actually need to monitor fibre at all. Many people (including Type 2's are having a carnivorous way of eating so they eat hardly any fibre at all. There is load of fibre in veg like celery and also soluble fibre in both beans and in oat bran.
I get plenty of fibre from the low carb leafy green veg I eat every day, but don't monitor it and wouldn't care if I had almost none.
3). The main electrolytes are Sodium, Potassium and Magnesium. You can use supplements or bone broth. I use a low sodium salt (like 'Lo Salt') but a supermarket own brand it is 66% Potassium Chloride. I also take a magnesium supplement. The most commonly bought magnesium supplement is Magnesium Citrate, but that gives me the trots so I take Magnesium Glycinate which is supposedly good for sleep.
4).,5), 6). My opinion of multivitamins/multiminerals is that they are both expensive and such a low dose as to be useless should you actually need them.

As a Type 2, the most important blood test is a regular Blood Glucose test, but I have no idea as to which blood tests are relevant to a VLCD. I suppose that if you aren't eating red meat then Iron deficiency is possible, similarly Vitamin D.

As a T2 who used a low carb way of eating (no calory restriction) for my T2D remission I can say that I lost between 1 to 2lbs per week and my BG levels went back to normal ranges almost immediately because I was only eating as many carbs as my Blood Glucose meter told me my body could handle well.

I hope this helps.