I think I can clarify some of the misconceptions here.
Premise 1 of the argument is deeply flawed. The main issue is the definition of 'objective'. Usually, objective means that something is independent of a mind. Things that are dependent on a mind (preferences, beliefs, etc) are subjective. So, if Craig is claiming that morality is objective, then he's saying that it isn't dependent on any minds. However, he establishes God (who is supposed to be a disembodied mind) as the necessary foundation for morality. (Divine command ethics) If God's mind is what anchors morality, then morality is subjective.
However, we can redefine objective to be more useful. Objective could mean verifiable by all people, a fact about the world, and not dependent on a particular mind. So, it is objectively true that a chunk of rock is denser than a chunk of cotton candy. Now, only in a world with at least one mind do any of these words have any meaning, but given some minds, all will agree with the conclusion. This makes the conclusion objective. A mind could not rationally disagree that the rock is less dense than the cotton candy.
With this definition in hand, it may be quite plausible that an objective morality exists apart from a god. It could also be possible that this morality exists, and a god exists. In that case, god is just another mind verifying that morality is objective. One could go about thinking of "objective" morality as the most rational actions that a group of agents would take. As an analogy, there may be a "best" way to play chess. If winning is the goal, it is possible (with a huge amount of computing time) to mathematically evaluate the space of all possible moves and determine which is best. The same could be said for objective an morality. We could evaluate all the possible actions that a society of people could take, and figure out the best method. It could be possible that there are multiple, equally effective methods. (This is basically the Sam Harris idea.)
I also noticed that people were confusing "objective" morality with prudential concerns or motivations for moral actions or duties. Basically, the argument is something like, "If there's no God, why not do anything that you can get away with?" This is a confusion of terms. Morality can be objective, and totally apparent to a person. However, if they disregard the objective moral rule, then they can act immorally. Just because morality doesn't provide some prudential motivation, doesn't mean it's not objective. In fact, I would argue that "moral" systems that are reliant on prudential motivators (carrots and sticks) aren't really moral systems. If someone says "You should help others, or I'll shoot you in the face" and you decide that it makes sense to help others, this wasn't a moral decision. It was a prudent, objective decision, but not a moral one. This is where the Kantian idea that morality has to be self imposed comes from. For this reason, people who are sociopaths, lacking all empathy, can't understand intuitive moral decision-making. They can only understand the prudential facts of a situation.
Premise 2 is also really bad. It amounts to, "Don't you just really FEEL that morality is objective and true?" This is an appeal to emotion, with no backup argumentation. It is an open question in moral philosophy if morality exists at all (error theory), or if moral feelings can be true or false at all (noncognitivism).
Finally, when Craig talks about evolution not being an explanation for morality, he's not talking about the actual behavior. He doesn't mean (entirely) that he thinks that altruism couldn't have evolved. He's saying that if it evolved, why is it moral? If humans evolved in a different manner, would different things then be moral? That's his point. Evolution can explain the behavior, but it doesn't provide a proscriptive basis for saying that something is moral. To argue the contrary would be the genetic fallacy.