your jack looks like a 2 ton. A normal 6" screw vice can, at a push give about 1.5 tons. The idea of the saddle tank is a good one. If you want to increase the output of the jack one method would be to decrease the size of the pump piston and cylinder. (All jacks seem to have the same size pumps, the load piston being increase in area to increase the output, so conversely, a smaller piston would deliver more force with less effort).
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