Casein content after curdling
It depends on how the cheese is made.

Whey will include a lot of the water soluble molecules of the milk. That means a lot of the sugar (and acid if it was fermented) will wash out. Any of the albumin from the milk will also wash out. Almost none of the fat will.

This means that it will be very difficult to calculate exactly how much sugar and protein are left in the cheese but you can get an idea from the type of cheese.

If made with yogurt, for example, the milk should have been heated before making the yogurt to allow the albumin to be bound up and not wash out in the whey. In this case the whey has almost none of the protein.

In many other cheeses, the whey does have a fair bit of protein in it. You can bring the whey to a boil and make ricotta. Weigh the ricotta to determine how much protein is not in your cheese.

As for sugar- If fermented, a lot of sugar is converted to lactic acid. The whey is full of extra sugar and lactic acid but a lot is left in the cheese as well- this is why aged cheeses like cheddar will get more tart over time. The bacteria keep munching on the leftover sugar. I don't know how to estimate the distribution of sugar in these cheeses.

A notable exception is a washed curd cheese like gouda. When these cheeses are made, instead of just draining the whey, the curd is washed in warm water several times. This washes out much of the excess sugar and makes a cheese that doesn't get tart as it ages.

I think the only way to know exact amounts of sugar would involve chemistry skills that I don't have.