II also believe a larger part of the Romanov family was involved in the Rasputin murder plot - an effort to exile/murder Alix would have been next.
I don't think that Felix told even half the story of Rasputin's murder in his book. I certainly agree with Radzinsky's explanation that Felix couldn't even shoot a mouse, and it would take an atletic Dimitri to shoot and kill him. Purishkevich in his book claims to have killed Rasputin. But he lies in order to save the Royal youth's name and honor. He also lies about the identity of the woman (Irina) that was the carrot to woe Rasputin to Felix's palace. He calls her Countess X.
So even after reading Felix's book we don't really know what happened that night. I actually wonder why Dimitri was so upset with Felix, since Felix's tale is not really accurate. Felix was nice enough to keep many names out of his book.
Alexandra liked Dimitri because he was cute, funny and fun to be with. So initially she approved of him as a match for Olga. However, Dimitri had a very loose and promiscuous lifestyle. He practically lived a double-life. Many believed that his friendship with Felix, at least in the beginning, was not all that platonic. It was this rumor that reached Alexandra and spoiled every thing. After that Alexandra simply wouldn't want Dmitri near any of her girls. I don't think Dmitri would have made a good husband to any of Alix's daughters, since they were all very naive, decent and religious. Everything that Dimitri wasn't. He would have been bored to death with them, and probably found a mistress right away.
By the way, Dimitri was not the only one fascinated by Michael's widow. Apparently she was one of the most fascinating, elegant and intelligent women around.