I wonder how the law addresses using something more powerful than that in those circumstances. I would guess that the law would hold that that would be about all he could do under the law...if even that. He (the father) would be viewed as the aggressor.
In the U.K. he probably would have been crucified for using the 2x4.
you watch this perp POS will have a scumbag lawyer that will SUE the father for beating him with this 2X4 and WIN. Only in California. Watch!
Here in Texas you could chase the SOB down the street and blow him away. No problem.