seems to me he was being treated much better than she was.
They gave him 1/3 of 50 acres and 20% of the company, was that worth more than the London flat they gave Sheila? I have no idea.
The grass is always greener on the other side.
She got a place to live in London. She didn't have to work for them to receive it. This meant she could use whatever she made working in the city for her food and utilities and they probably gave her money if she were short in such regard. Jeremy was jealous of this he wanted to live in the city.
While he stood to get the business that would only be if he ran it and farmed. If he walked away he only owned 20% and probably could not sell his shares to anyone so it would be of limited value till they died. If he walked away after their death he would get 60% while Sheila would get 40%
He would only get 100% if he continued doing the work and that 100% would be simply the profits from running the farm. If he sold the company then he would get 60% of the proceeds and Sheila 40%.