Some good points.
I don't think the things you mention are necessarily contingent on rebirth though. Why does becoming a mendicant have to have anything to do with rebirth? I think that is one thing which doesn't while others would be more tricky to explain away.
Even the explanations of the benefits from the Buddhist perspective, from what I recall, do not appeal to the supernatural. It is simply living humbly and I do remember now specifically the text stated the Buddha insisted on it in order to highlight the intertwined nature of the bikkhu and the lay people where one hand washes the other. The bikkhu gives insight for the lay person when the latter asks for guidance and the lay person gives the bikkhu food to survive. Nothing of that has to have anyhthing to do with supernatural explanations.
I agree that the traditional answer is going to be 'no' on all counts but of course they are biased and not able to give an uncoloured opinion.
As to the 'no selfness' being contingent upon rebirth I again don't think it is necessary. Lots of neuroscience, and this is a point Sam Harris makes when discussing the topic, has confirmed there is no 'I' to be found and it is just a social or cultural construct. So it can easily be explained from an empirical standpoint. To actually have some huge insight just from that data is another matter.
As mentioned earlier though, the same spiritual experiences have been documented from vastly different cultures and through the lens of their own religions and worldviews. This means that like the idea of God there is no one right answer. This then means that all the talk of reincarnation is not necessary to have such spiritual awakenings as the Christian mystics managed just the same and do not hold those same beliefs.
What should be done is to read through the different mystical experiences from each culture and religion and look for the common threads. Joseph Campbell apparently has done this in his work Masks of God. I have started reading it but not gotten very far in it and put it down after not many pages as I had another one of my downswings in motivation for the stuff again but seems I might be on an upswing again now, so maybe time to take another look.
Like with the Jungian archetypes, of which I know Campbell was also inspired by quite a bit, the spiritual experience is a human experiences, and not exclusive to one particular religion. The shallow or pop analysis of Buddhism states it is to have these experience without the religious dogma of the orthodox western religions, but when you scratch the surface you see Buddhism is steeped in its equivalent dogmas. It may just be a little more palatable for some as there is no solid "God" in their doctrines but all the devas and their antics and rebirth as just more of the same.
I would hazard a guess that it is the rituals of whatever religion not the actual content of the mythologies that allow the transcendent experiences. The question then is how to recreate that roadmap of the path to attainment as one who does not believe in any particular one? Can the same states still be achieved if one only takes them as allegories rather than realities?