Is it religiously permissible for a partner to take half the profit after he bought for himself more land than agreed upon, and then sold the partner's share at a profit seven years later and took half of that profit?

What is mentioned in the question is considered a valid Mudarabah (partnership). The share of the agent in the profit of the Mudarabah is not restricted by a specific limit; rather, it is according to the agreement, as Al-Khiraqi said: "The profit is according to what they have agreed upon." The agent is entitled to this share after returning the capital to its owner, because he is not entitled to take anything from the profit until he returns the capital to its lord. If a profit appears in the capital, the agent becomes a partner in it according to his share of the profit. As for his purchase of one hundred feddans for himself, it has no relation to the Mudarabah.