the only thing that i would punt is the flow tec pump.The only way for you to get the pump from drawing air is to insert a tube back in the well so you are not putting a vacume on the well casing itself. For now i would get the poly pipe back down the well maybe 1 foot off the bottom and pump the well of with a gas pump.If its drawing air at that point then you are probably taking more water out of the well than what it will produce. Under that circumstance i would normally tell someone to bang another section in but seeing that you have a compromised coupling i would deal with what you have and get to developing the well. A well pumped pumped sand free at a high rate will pump sand free at a low rate. With that in mind pump this well off at a higher rate than than what you will use for your house or irrigation.I would pump the well with a gas pump and periodically throttle it up and down so the colum of water is being moved up in down in the casing. This surges the screen and breaks up the fine sand that builds up around the screen.You will get to a point where no more sand will come through as you are pumping. Once you get to that point i would do a flow test to see what you have for water. Take a five gallon bucket and fill it with water being pumped from the well. Time it to see how long it takes to fill to the five gallon mark. Take that time and divide it into 60,multiply that figure by 5 and thats your gpm.If you dont have the amount of water you are looking for i would consider another well but go easy on tightening the couplings this time. Another thing that i am concerned about if this is going to be used for drinking purposes is where that coupling is broken. You could get some surface contamination in the well.