hydraulic pump problems

As for the tractor running wild while throttling up... It sounds like you have a throttle linkage binding. Usually on a late B it binds either in the hole in the hood support underneath the gas tank, or perhaps the cotter pin is missing on the carb end of the linkage allowing the linkage to sink too deep in the carburetor.

If the choke needs to be out all of the time you could have a couple problems. Having to run with the choke on means you have a lean mixture problem. Did opening up the idle needle help?

This may be because of a vaccum leak. Get out an aerosol can of WD-40 or starting fluid and spray the connections between the carb and intake mainifold, and then again all around the area where the intake meets the cylinder head.

If your tractor surges at idle it may be possible that you have plugged idle passages in the carburetor. You should get a Robert's carburetor video if this is the case. The video has great insctuctions on how to work on your DLTX carburetor.