Welcome John to a hobby that will take 5 or 6 lifetimes the learn about. May I make some comments, from my experiences, which you might find useful SUGGESTIONS ?

1. Weeds in small quantities can be useful for sheep, but they are designed to eat pasture. They will do better on pasture, and they will enjoy it more if it is nutritious.
2. Pasture is able to grow without the soil being the correct fertility for it. But it will not be as nutritious for cattle or sheep as it could be, and weeds will grow in preference. To grow pasture needs pasture fertility, and forestry tree fertility. So sort the fertility out, especially acidity. Lime application by truck is the best way to address this.
3. Weeds in excess will be poisonous, andd sometimes the excess is very small.
4. To rapidly convert forest to pasture requires the stumps to be ripped out, so that fertiliser can be more easily spread. If the lime is to be spread by air (very expensive), then the stumps will rot away in 4 or 5 years.
5. I spread fertiliser (super phosphate and the likes) by hand on my steep 20 or so acres.
6. I have wasted my time with an orchard, which is rather silly in Nelson, with no irrigation. But it does mean I can still get Granny Smith apples (of poor quality). Orchard trees need different fertility and minerals to pasture, so I have to be careful which animals go into the orchard.