McCall supposedly botched the arrest of the ex-con because he didn't ask him any questions before searching him. Unless California laws were very different during this time period (early 1970s), the wife's claim that the felon had a gun in his waistband should have been plenty of probable cause for the search and seizure.
There is no smoke emanating from the car itself in the aftermath of the car explosion, it all coming from the exterior of the car.
After eight years off the force, McCall or any officer returning to duty would have to undergo some classroom training covering search and seizure and interrogation. McCall seems unaware of any changes since he left.
After McCall cuffs Frank Young and puts him in the car there is no indication that McCall has taken Young's gun.