No - just moderately disgusting. The lemon (or any acid) will cause the milk to curdle. Very few cultures like curdled mik. This falls into the "harmless yet unpleasant" category.
it will make you feel a bit queasy, but it is harmless
Yes! Tea with lemon and milk is delicious =P You could also use half and half for a more "creamy" taste. You can add honey also for sweetener. Hope this helps!
Milk has calcium and vitamin D. However, you don't have to drink milk. You can take supplements or eat other foods rich in calcium. 15 min of direct sunlight can provide enough vitamin D for a day...
Hmm... I'm not an expert on snakes, but I don't think the Milk snake got it's name by drinking milk. I don't think there a lot of snakes that do, if any.