I believe I understand your position better now.
> Joseph was to give Jesus his name, and it was culturally regarded as the father's right and duty to name the son (though legally either parent could name the child). So this tells us that Joseph was exercising a fatherly role
Right, my skepticism lies solely in the claim that this “fatherly role” is enough to ascribe to Jesus his Davidic ancestry. Your claim is that Mishnah Kiddushin 4:5 allows Jesus to enter Joseph’s line since both Mary and Joseph are allowed the right to marry as two Kohanim. However, my argument is that the lack of necessary “proof of parentage” only applies to a biological offspring, and thus Kiddushin 4:5 is irrelevant to Jesus’s genealogy, as he is anomalously “accepted” by Joseph as a son.