Pump stuck in borwell in Vidarbha : Need advice on retrieving the pump and retaining the bore

I drilled a bore , 6.5 " dia. with casing pipe for 20 ft in hard black rock in the Vidarbha region. Struck water at 80 ft (approx 1/2"). With yellow soil for aproximately 5-6 ft at 250 ft deep. hard rock till 350 ft. water at 350 ft , 380 ft, 450 ft. as per driller he has neverseen such water source before at 500 ft. There was some mud at 510 ft. drilling stopped at 510 ft.

After drilling , we procured a 25 stage, 5 HP pump, 2.5" HDPE pipe and best quality power cable.

Before installing the pump, when we checked the bore we observed siltation upto 450 ft. So we lowered the  pump upto 400 ft. Pump ran continuously with out drying, we operated pump for 6-8 hrs a day. No problem.

One day , we observed that electric cable was stretched. we pulled it and tied it properly. Next day again we observed same phenomenon, but observed that cable is broken. We doubted the improper joining of the cable with HDPE pipe. because of self weight cable might have broken. We tried to pull out pump with the help of HDPE pipe. it came up to 270 ft but then stuck. We tried pulling with bullock cart (to pull pump out), it did not move. The pump is jammed so badly that it could not be removed even with chain pulley block arrangement which pump mechanic set up.

My expectation.

Ready to lose the pump but not the bore. I have gone through almost all related  Q & A on this portal about casing pipes. pebbles filling, but I am confused. I would like to request for suggestions / responses that will help me retain the bore.Also contact information of suitable experts to do a hands on evaluation in the Vidarbha area will be appreciated.