The first one sounds pretty textbook: save the many before the few. The second is well within standard operations for a rogue: if you killed the giant with "well-placed sneak attacks," that implies attacking them earlier would not have killed them and thus would not have done anything to help the other characters (unless the DM runs them like dumb MMO monsters, at which point you get to try kiting them yay).

The difference between lawful and chaotic is that lawful is beholden to others (often a ruling body or set of principles from their culture), while chaotic is beholden to self. A common problem is a "lawful" type defining their set of principles as "do whatever I want," and some might say being "pragmatic" is the same thing, but it's not. As de-facto party leader your job is to make the calls: sticking to the plan even when others have abandoned it upholds the principle of the matter and is indeed the standard lawful response. That fact that it was your plan changes nothing.

As for being good, that doesn't mean stupid or doormat either. You don't have to throw yourself into harm's way for every idiot that passes just to keep the tag, just help enough people in general. You don't stop being good because you failed to personally rescue enough party members, just like you don't stop being evil because you helped a few puppies. If anything the party should count the least for "alignment points," since they're both highly competent adventurers who can take care of themselves, and have a close personal relationship with you that allows for exceptions to your usual demeanor. Evil people have loved ones and comrades but they're still evil, good people can let their friends rush into danger and even die (in fact it's a common trope that you must let them do so in order to respect their autonomy).