Yes. on both counts… … Although at that point, after Anikin killing all other Jedi, I would think it would be 100% self defense, and in defense of the republic. So maybe only yes to B. I think Obi was heartbroken as well. Anikin was bascially his family.
Just some of my thoughts on this action and the Jedi/Sith code in general. (Yes I’m a total nerd who’s read a LOT of Star Wars material).
In the novelization it says that Ob-Wan considered finishing the job, but decided at that point to let the Force do its job. Remember he says “I will do what I must,” and that’s indicative of Obi-Wan’s (and the Jedi in general) approach to the Force. Anakin wasn’t a threat at that point, and was indeed dying. It’s not so much the killing that is inherently wrong, it’s using the Force to push the hand of nature too much, and killing is an obvious and egregious example of that. Obi-Wan had done enough, in his mind, and it was time to let the natural flow of the Force, of nature, take over.
This is also hinted at with Palpatine’s discussion with Anakin in the theatre when he mentions that the Force can be used to do things that some consider unnatural, such as preserving life indefinately. In the Sith mindest, there really isn’t a “Dark Side” of the Force per se, in the sense that there’s some distinction between types of Force power; that’s really more of a Jedi philosophy and their view is pretty unique to them. The Sith speak of the Dark Side only in reference to the Jedi’s beliefs about it, but really it’s a pretty foreing concept to them. They understand love, and other positive emotions, they just believe that the individual’s will trumps all else, and if you have the power to shape the world around you, you are obligated to do it (“it is your destiny”). It’s a very “Will to Power” kind of faith, and one that isn’t as simplistic as the Jedi make it out to be. They have empathy, they aren’t sociopaths, they just believe that everything, even emotions, are supposed to serve the individual will, which is why they’re willing to tap into their hatred and anger because it gives them more power with the Force.
For the Sith, the ends (personal power/godhood) justify the means (anger, rage, betrayal, and yes, even love can provide the push necessary to truely warp the Force to one’s will). Personal power is the holy grail of their faith, not simply a short-sighted desire to dominate (“Power! Unlimited power!”) For Jedi, the means (peace, calm, following natural law) are the ends. The Jedi don’t study the Force because they want cool magic tricks to defend people with, they do it because it is part of nature, and they seek tranquil communion with all things. Being a Jedi isn’t necessarily about being a nice guy who gives money to charity and loves puppies, it’s a whole philosophy about finding one’s place within the greater tapestry of the universe, and acting in concert with nature (and the Force), and not against it.
The Sith are undoubtedly evil, just not in the simplistic way they are portrayed by the Jedi, and the Jedi are not necessarily the noble heros that everyone trusts and loves. In fact, the Jedi are among the most mistrusted people in the galaxy in the stories outside of the movies, and even within them.