One beaver needs:
2 Water per day
2,5 Food per day

All kinds of food seems equal.

How i tested it:
Starting settings was 100 beavers, 10.000 Food, 10.000 Water
After 9,7 days 2500 Food and 2000 Waters was used. So the actual consumption is a little bit higher.

Small Water Tank: 30 Units
Large Water Tank: 300 Units
One full Block of Water: 5 Units

Note: A Dam blocks water at a height of 0,5. Which means you dont get a full block of water. However you could replace it by Floodgate and try to manually raise the height to 1,0.

Water (unless in a tank) does evaporate at a rate of 0,25 units per tile and day or 0,05 height units per day. This means a full block will stay for 20 days in dry season. A half block for 10 days.

Tested with the stopwatch. So this numbers are not perfect.

Pumps
One Water Pump generates 1 Unit of Water every 7s.
One day is around 465s and with a 16 working hours you should expect 44 Units of Water per day. Which means the pump can supply ~22 Beavers.

Farms

1 Potato will yield 4 Grilled Potatos. One Grill will supply ~62 Beavers.
3 Wheat will yield 15 Bread. One Bakery will supply ~68 Beavers.

The farmhouse has 2 workers and can take care about roughly 80 tiles of carrots, 120 tiles of potatos or 200 tiles of wheat.

Rule of thumb: One Water Pump and a Farmhouse with 80 carrot fields can supply ~20 beavers.

Folktails procreation need at least 2 beaver and one free slot in a house.*
This happens only at night and the chance is increased by 50% if the need "Social Life" is met.

However Iron Teeth do not really need houses. They only need breeding pods to procreate.
One pod needs 5 Water, 5 Berries and 5 days to "create" a beaver child.
The normal lifespan is 60 years.
This means one pod supports a population of 12 Beavers.
If you have the maximum lifespanboni of +115%, then one pod supports 25,8 Beavers.

*need confirmation