It is nice that you are able to reach these conclusion with seemingly ease. I don't quite see the sin as blatant.
Yes, some people don't see OT law as binding as others. There are churches full of homosexual couples. There are theologians who don't think sex between a mother and her son is wrong, or sex between a brother and sister.
There is a reason this particular part of the Board is called "The law of God".
Perhaps there are no clear answers, and everyone should be left alone to decide these issues for himself. I see that as chaos, you may see that as Christian liberty.
On my side I have 2000 years of tradition, plus clear Scripture. Feel free to post your conclusions. Perhaps you may convince more people that I that your view point is closer to the Christian ideal, if that is your intent. Just be sure to be consistent, and don't stop at half-siblings.