Tons of hay per acre varies widely by region and even farm. Even poor hay ground will generally produce 1 1/2 to 2 tons an acre. If you have to have someone else cut and bale your hay be forewarned the cost is often about 60% of the hay harvested so that might put you as low as just over 1/2 a ton an acre if you went that route.
As for animals you have pasture grazing and then you have winter hay. With goats and sheep you figure 4% of body weight a day in hay not including waste, and there is always waste, I usually calculated 15% to 20% waste with my goats and sheep.
Cattle and horses are at about 2% of body weight a day in hay. ie a 1,200 pound horse needs about 24 pounds of hay a day or 720 pounds a month, I always calculated 1/2 ton per horse or cow a month. Here winter freezing and snow last about 5 to 6 months a year, best to always calculate on the worst case scenario so for me about 3 tons hay per horse or cow a winter.
You can allow your animals to graze hay fields after you hay them in June/July allowing you to use them as both hay and grazing.
If you fertilize hay (not a bad idea as it makes it much more saleable) you can potentially get harvests of up to 3 or 4 tons an acre dependent upon the quality of your
land. Whether the animals per acre is based upon what you can get by with it is hard to say, the amount of animals per acre varies wildly between different areas and even between different properties within the same area.
One must also consider the potential damage that livestock do over time to a grazing area. My neighbors run 6,000 head of sheep on about 800 acres, the first few years went well, but as sheep eat the
roots of the grass they have killed off all of the grass and now they get about 1/4 the amount of grazing form that land that they did originally. For me raising
milk goats I found that goats are not really designed for "grazing" they are browsers and do not eat the plants into the roots and they do better on pastures, though they prefer bushes and forest eating over pastureland. Different livestock have different effects upon pastureland.