I think Jack was afraid to leave any sort of evidence, because he doesn't know how much Adam needs to be remembered in order to survive. That's why he didn't tell himself what happened.

And re CPR: No chance. Owen was hit in the aorta by the looks of it, in which case the human body will bleed out in thirty seconds. He was effectively dead by the time they took down the doctor guy and reached him. There's no point doing CPR on a heart with a hole in it - that's first aid for a stopped heart, not a ripped-up one. (I worked nine years in a cardiac surgery theatre, there wasn't a thing they could do, and Martha's experienced enough to know it.)