Why don't you do the first obvious thing.....like was suggested earlier.....have the well blown first and foremost. In my area, a well that has set for that long without being used, would be blown first. If you don't know what that is.....you get a big compressor that pumps gobs of air with a long air hose. Put the hose down the well and turn the air on......it will blow all sorts of crap out of the well and clean the casing as shiny as a babies butt. Then try your pump and see if the well will produce the amount of water your looking for.
I just know one thing, which isn't much, wells that are not used for a long time tend to silt in and do not produce.