Homemade Yogurt — Caloric Conundrum

So, I have a problem.

I made yogurt, thinking it might save me a few dollars. But now I'm realizing after probably 4-5 days of trying to do the math, there is no easy/good/reliable way to calculate the calories or macros for homemade yogurt.

Here's why I believe this.

I made yogurt from 2% milk. 2% milk has ~50 calories per 100g, and 3g protein. Acid Whey, which is the whey you get when straining yogurt, has ~24 calories per 100g, and ~1g protein.

You'd think I could just take the calories and protein from the volume of milk I started with — Let's just say 1000g for example — and subtract the calories and protein from the amount of whey I removed and weighed during straining — Let's say 600g — and I would have the final calorie and protein numbers for the strained yogurt.

Using our example numbers, we would start with 500 calories and 30g protein from the 1000g 2% milk. We would drain off 600g of whey, removing 144 calories and 6g protein. This would leave us with 400g of 2% Greek Yogurt, with 356 calories, and 24g protein.

A normal serving of 2% Greek Yogurt, according to my brand-of-choice Fage, is 200g. So, a serving of our homemade 2% Greek Yogurt would be 178 calories with 12g protein.

Here's where I ran into trouble.

2% Fage comes in 200g tubs. Each tub has 150 calories, and 20g protein. The ingredients don't list anything but the dairy, and the live cultures they add to ferment that dairy. For every gram of protein in 2% Fage, there are 7.5 calories. Our homemade version has almost double that, at ~14.75 calories per gram of protein.

Here's where it gets really tricky.

The number of calories per gram of protein goes down as you remove whey. So just remove more whey, right?
Actually, no. Even if you removed 1000g of whey from 1000g of 2% milk, you STILL wouldn't match Fage's calorie-to-protein ratio. 1000g of whey has 240 calories and 10g protein. Subtracting that from our 1000g of 2% milk ( 500 calories, 30g protein ) results in 260 calories, and 20g protein. That's 13 calories per gram of protein...

It also isn't possible to remove 1000g of whey from 1000g of milk, but given the information we have about protein and calories in whey and milk, that shows us the lowest calories-to-protein ratio that could ever be theoretically possible.

So, my questions are these...

How are we supposed to calculate this stuff?
Has anyone ever done an accurate nutritional analysis on 2% yogurt by itself with no additives and no whey strained out?
Does milk completely switch up its macros when we ferment it, even if it doesn't lose mass?
Are Fage's nutritional facts incorrect?