Thinking about Armand saying "I do not see the waste Mr. Molloy sees."

He wasn't talking to Daniel then like the other two times he said "Mr. Molloy", he was answering Louis. Which is oddly sweet because he's showing his lover support but doing so in an incredibly tactful way: "I do not see the waste" more like "I do not think you're wasting your immortal life and I will never ever think that."

But they're also dancing around the topic of why Louis did not turn Daniel in the first place when he actually seems to want to do so in the present or at least is considering it: why not back then when Louis was apparently lonely and living in a dump? Why wasn't Daniel considered worthy of the gift then?

Well, it could be because Louis wasn't actually alone, he was involved with Armand (did they recently reunite or did they actually fall back in love shortly after the first interview when Armand saved Daniel?) so you know he wanted to actually discuss it with Armand first but then things got out of hand.

It's more likely from what we know about Louis that because Daniel was angry and hurt and suffering, Louis knew that Daniel was really just after the quickest fix going. However that would have destroyed Daniel: it would not have made his problems go away. It would have wasted Daniel's potential. Daniel eventually picked himself up, dusted himself down and lived his life to the fullest without any supernatural intervention whatsoever.

It was not a waste to save Daniel's life in the 70s, it was their gift to him.