Teresh

The problem for that is that for purposes of Jewish law an adoptive father is not considered the same as the biological parent. If a Jewish family adopts a gentile child, even as an infant, that child will still need to be formally converted in order to be considered a Jew by Jewish law.

The status of one being a Jew is passed down matrilinearly according to Jewish law, but status of the Kings and the Priests (Melekhim, Kohanim and Levites) is passed down patrialinearly. This also applies to an adopted child--An adopted child, regardless of whether or not his adoptive father is a Kohen or a Levite, cannot gain the status of either. Moreover, if the child is a Kohen or a Levite, he does not forfeit this status simply by his adoptive father not being one.

Assuming we're willing to accept the virgin birth as true, then it's impossible for Jesus to have been the Messiah as he would need to be of the line of Kings and that would require a biological father. However, if we are willing to forgo that belief and rely on the more realistic idea that Jesus is actually the son of Joseph and Mary together, then it is much more plausible that he could have been the Messiah.

The issue here is that while it could have been Mary's genealogy, it says Joseph. More importantly, it also does not matter what Mary's genealogy was for the purpose of Jewish law--Mary could not pass down Jesus's status as a King because that is not something females of that line inherit.

The Jeconian line would be the main problem with the idea that Joseph was a King under Jewish law because of the curse. There is some midrash that says that the curse was lifted, but there is nothing in the Tanakh itself that explicitly supports this claim so it's hard to tell.

Yes, but that's through Mary by your intepretation, something that doesn't hold up given the above. Again, though, if we're willing to disregard the virgin birth idea, it's all the more plausible.