Whatever he was hiding from, it finally caught up to him. I think he was probably hiding from creditors, or possibly the court system, when he assumed a fake identity no telling how many years ago. He could have shelled out a few hundred bucks and gotten a drivers license and social security card issued in whatever name he wanted via the black market.
13 felony charges is a good start, but I think even the D.A. knows that the majority of those are just fluff that can be used during plea negotiations. Any charges that can be brought by the State of Calif., and not by A, have a better chance of sticking. I'm surprised he was stupid enough to take her across state lines, because that always gets the feds involved when there is a minor in the mix.
A appeared to be such a willing participant in this caper, I still highly doubt that she's going to be willing to implicate Max in any way. If they were able to add a couple of charges against her, basically turning her into a defendant, it might help to get more cooperation. Those charges could always be dropped of course if she was willing to give full disclosure about what happened between her and Max. It doesn't look like they plan on taking that approach however.