Get some local experienced help if you can; these problems are hard to troubleshoot at distance.

You can isolate the problem by running the engine in a test station or by feeding the engine with a provisional second tank located higher than the carburetor (hold it with rubber bands over the fuse), or even by the fuel jug also high.

That way you will know if the problem is in the tank or in the engine.

Whatever you do, please, be very, very careful around that propeller.
They bite frustrated RC pilots easily.