Another thought after looking at the parts illustration for your tractor's fuel system.
You are having this issue with 1/2 tank of fuel. Fill the tank and see if the problem stops.
Many tractors including yours use a lift pump, i.e. a pump to feed fuel to the diesel injection pump.
When the fuel tank is full, if the top of the tank is above the height of the injection pump, fuel will flow by gravity and satisfy the engine's needs.
At other times, such as driving on slopes or with a partially filled fuel tank, the height of the fuel level drops below the injection pump and a lift pump is needed to deliver the fuel.
When working on gravity, the lift pump's internal valves allow the fuel to flow freely. There is no switching on or off of the lift pump but if yours is failing it could explain the stalling with less than a full tank.
Dave