How might it be possible that the water we drink is from the same age
as the dinosaurs?

water is reused. The water we have on earth doesn't actually replenish but rather goes through the the water cycle. The same water that was in the Ground will end up in the clouds making it rain, or in the Ocean. Whether it is condensation, precipitation, evaporation or percolation, it is the same water going through the water cycle.

1. The repeating units in a fatty acid are just carbon atoms. They usually have two hydrogens attached, but can have one (in unsaturated fats) or three (at the end of the chain). This is simpler than nucleic acids and proteins. 

2. Fatty acids are used to make phospholipids, which make up most of the mass of a cell membrane. The fatty acid portion of a phospholipid is very hydrophobic (does not mix with water).