Beginnings and Endings only have meaning within the context of Time. Remove Time and there are no Beginnings and no Endings. Time began with the Universe. Of course, it's difficult for us to imagine Timelessness (aka Eternity), but it's just as difficult for us to imagine a Universe with more than three physical dimensions.
Yes, they only have meaning within the context of time. This argument of god being outside of time is no different than the argument that he has always existed. It still has no evidence to back it up, so requires none to refute, so here's once again my refutation that your god is outside of time, and I will give the exact same amount of evidence you have given: No he isn't.