That is the question. Have nothing more to add.
A half gallon of whole milk makes about 10 ounces of paneer (From the kitchn). So conversions and cross-multiplication later, about 670ml of whole milk will make about 100g of paneer. Since it's not an exact science, how about using a quart (946ml) of milk, 2 TBS of lemon juice and 1/8-1/4 tsp salt. That should yield about 140g of cheese, giving you a little bit left over.
This answer is assuming 3.5% butter fat for the whole milk(UK regulations).
Paneer is between 25% and 27% butter fat.
Since the ratio of fat in milk is mass(or weight depending on the country) per unit volume we can quickly calculate that it would take between 715 and 775 mL of whole milk (assuming all milk fat is captured in the curd) to yield the 25 to 27g of fat that we need for true paneer.
This calculation is even better than a rough recipe because you can gather your curds and press out the liquid until you reach your magic 100g number, ensuring that you have made real paneer and not some other farmers cheese (such as Tvorog which has a higher moisture content or Branza\Brynza which has less before brining.)