I apologize now for this being lengthy but I wanted to provide as much info as possible.
I have an above ground 1 hp pump on a 2 inch well with a bladder type pressure tank. The well was drilled about 28 years ago before I was at this house so I don't have info on the depth of the casing or water table.
About 4 years ago I installed a spinkler system in my yard with 4 birds on 1 zone and 5 birds on the other. Everything worked fine. A few months ago I had the pump power off and drained the tank to add some air as I have a small air leak in the tank. I also spent some time trying to repair the leak. Once I turned the power on about an hour later, I had lost prime in my pump. I re-primed and all was good for now. I called my pump repairman and he came out and replaced the foot valve at the bottom of a 40 foot drop pipe which was either 1 inch or 1 1/4" galvanized. A few days later the power was off again and I lost prime. I called him out again. This time he told me I probably had cracks in my galvanized well casing.
He moved the "packer"?? or K-packer?? further up on the drop pipe to the joint between the two 20 ft. sections of 1 1/4" to bypass the cracks or holes in the casing. This kept me from losing prime but now my volume has suffered greatly. The water volume in the house is O.K. but the spinklers only spray about 10 feet once the pressure tank is empty. I am told I lose volume for every so many feet the packer is moved up from the bottom of the drop pipe.

He says my only option is to drill a new well. I hate to question his knowledge but for $3K-$4K I feel I should get another opinion. Should I try moving the packer (sorry if this is not the correct term) a few feet down to regain volume? He said it had to be above the casing holes but I don't know how he determined where they are or if he just guessed. It appeared he just moved it to a convenient place where the coupling joined the two lengths of pipe but I am obviously not the expert so that's just an observation. I have access to a boom truck and I am considering pulling the drop pipe myself to try replacing everything before drilling a new well. Would it pay me to try cutting the drop pipe at about 30 feet down, re-theading and reinstall the packer at a lower level? Or, do I give in and call the well driller? Thanks for any advice.