Ah the ole "Paul vs. Jesus" allegation. I won't even address that one, except to say that Christ crucified is indeed quite a stumbling block.
But regarding the "...only to the lost sheep of the house of Israel" passage is Matthew 22, when the Savior healed a Canaanite woman... a gentile.. whom he called a dog, and then praised her for her faith.
Yes, we Gentiles are the "lost dogs." And the God of Abraham, Isaac and Jacob is pleased with us when we believe in Him and in His Son.
And as we have seen, some have a different understanding... ie.. that God is only pleased with a person if he is of the right blood... ie, a Jew... even an atheistic Jew.
Healing a gentile woman is consistent with his message of compassion. Would you not help a dog too? Do we not praise dogs for their faithfulness? But that's not the same as the reason he said he was sent. He made it very clear why he was sent and where he he didn't want his disciples to go, and it wasn't for gnetiles.