My understanding of the leaven parable is that adding leaven to flour makes bread grow faster, which is like the fast spreading of the kingdom of God from small beginnings. Are you saying the kingdom of God is good for nothing?

No, I don't know why the tabernacle was covered with gold. In looking it up, I see that Maimonides said it was to offer an alternative to the golden calf, to make God seem at least as important (which would still have been somewhat idolatrous).