He flew with 250 Sqd and then 112 Sqd. I don't recall any mention of incidents of Caldwell shooting opponents in parachutes in Mediterranean Air War vol. I and vol. II.
The wiki gives the killing of P/O Donald Munro in his parachute (which is supposedly the reason for Caldwell's shooting enemy pilots in their 'chutes) occurring on 4 July; but he was shot down and killed on the 18 June. I will have do check, but I don't remember Shores mentioning any incident of 'chute killing on the part of the Germans on this date.