Personally I think it means that Naruto doesn't want to TRY to kill sasuke, since Naruto can't exactly kill sasuke cause IT and well he wants to save him, sasuke understands this as well, Naruto also understands sasuke can kill him, basically if they both hold back the one with greater power usage will kill the other that is using less power urges. The best way to try this is to assume Naruto truly feel that he doesn't want either of him or sasuke to get killed.
As for the Naruto soloing kaguya that's explainable since saauke is yin which kaguya can counter that but Naruto is yang even Naruto realizes only taijutsu can work and with the tail beast assistance it works better. Sasuke just had the less efficient power against kaguya, if yin worked better then right now sasuke fans would super wank sasuke, but I like the development of both Naruto and sasuke.