Thanks for your query Based on the findings you have stated It appears that you had Hydronephrosis
on left side due to stone in Left Ureter and that is the reason your Urologist has put a Double J stent to decompress your left kidney.Your recent USG does not show stone now indicating that it may have passed down.Since Double J stent is still there USG will show hydronephrosis as long as stent is there and it will take two weeks to come to normal after removing the stent.So there is nothing to worry about.
As regard Enlarged Prostate
you have to consult Urologist
to decide the management of the same whether medicines or endoscopic surgery
As regards his all Bladder stone
since he does not have any symptoms related to Gall Bladder stone you can leave it alone as these are silent stones.