Sure but we will never know if Ebenezar's influence could have saved his daughter, it never came up.

Margaret was never caught by the white council so Eb was never in a position to intervene at his daughters behalf. For that she first had to be caught.

Given that he seemed to have a pretty negative view of the Council even /with/ his experience living with Eb, I'd assume that he'd be at least as distrustful if he'd learned about their idea of "justice" prior to being caught by it.  The real catch would be that he'd still need somebody to tell him about them ahead of time.  Which, now that you mention it, is a little conspicuous on Lea's part.  If she actually thought warning him against them was in his own best interest, she'd have been bound by her Godmotherly duty to warn him.  It's a little telling that she did did apparently believe that turning him over to them was the best thing for him, either to be taught by them or to simply learn to Survive them (or both).  But she must have had a reasonably strong confidence that they wouldn't actually kill him, or she'd have warned him when she had the chance.

Murphy becoming Molly's hand maiden for Harry's sake? Not bloody likely.

Not to add to that, but why have we never seen Harry get magical medical attention when he gets banged up? Which is at least once a year. Always at home, always Butters because either he doesn't want to mess with the IC machines or because he doesn't want the gunshot wounds reported.

The bracelet helped with the pain but didn't Eb rub some sort of cream all over the hand as well?  I don't remember but thought he did.  As for why he doesn't always use magical medication.  My guess would be that just like only one person on the Council can make enchanted swords, magical medicine is probably rare to come by and only specific people like LtW can even make it.