I think what said in #4 is probably right. Mary is a descendent of David, and is Jesus’ biological mother. Joseph is a descendant of David, and is Jesus’ legal father. So Jesus has both a legal pedigree and a blood relation to David, and the right to inherit his throne.
Joseph is a descendant of David, but from a line cursed by YHvH.shalom b'SHEM Yah'shua HaMashiachIt is YHvH's WORD, you might want to look it up.