LF – 1. As pointed out before, you are wrong about point #1. Perhaps if one could be CERTAIN that she wouldn’t believe him, you would have a point. But in this case, there is absolutely no reason to be certain that she would not believe him. Why shouldn’t she believe him?
In any case, he obviously thinks that she could believe him – the whole reason he said this was in order to convince her that it’s true and get her to believe that it’s true!!! So he can’t then turn around and say that he doesn’t really think she will believe him anyhow!
2.You are confusing things. I think that what you are trying to say is that if I am not certain that he is speaking Motzi Shem Ra, I can’t accuse him of speaking Motzi Shem Ra. Even if that is true, that is not the case here. The doubt does not lie in whether or not he is speaking Motzi Shem Ra.
If someone says something that he does not know with certainty that it is true, he has been over on Motzi Shem Ra EVEN if we find out afterwards that it happened to have been true. The fact that he said something that he did not know was certainly true makes it Motzi Shem Ra whether or not it was in fact true.
So he is definitely over on Motzi Shem Ra and I have an OBLIGATION to tell him so (see my Shmiras Halashon thread).
I hope that was clear. I know the grammer was a bit off, but my logic wasn’t. Let me know if you understand what I wrote or not.