A. since the reason of the YIBUM is LIVNOT BAYIT LACHIV how can U'LEKAHA become SHLO KEDARKA? There is no why to establish home in this why?
B. Simmilary: how it comes that he intended to come on BE'EMHA? Again, there is no why to establish home in this way? C. Continuously: in daf 54B THE GEMARA SAID THAT if a man come on BE'EMHA he sentenced to death - how that setteled with B above (and you can't say that this is KIDUSHIN BEHAYAVI LAVIN?A. The Torah commands that the act of Yibum be performed in order to fulfill the Mitzvah (Devarim 25:5). It does not require that it be done in such a way that the brother's home be built as a result.
The Gemara requires that in order for there to be an obligation of Yibum, both parties involved must be able to have children (TOSFOS 20a, DH Yavo). The Torah does not require, as part of the Mitzvah, that a child be produced. In fact, the Gemara explains the verse discussing the son which is born from the Yibum union (Devarim 25:6) not to be discussing the child at all, but to be discussing other laws of Yibum, such as which brother is obligated to perform Yibum (see Yevamos 24a).
B. True, he did not intend to produce children in this manner, but he did end up doing an act , unintentionally, that might fulfill the requirement of Yibum. And, as we wrote above, having children from the union is not a requirement for fulfilling the Mitzvah of Yibum.
C. In B above, he did not do the Isur. Even though he intended to do it, he is not held accountable if he did not accomplish the Aveirah. The Gemara is trying to determine whether the verse teaches that he is Mekayem the Mitzvah of Yibum with his act, despite the fact that he did not intent to do the Mitzvah.
Sorry for the delay in answering questions.
Y. Shaw