Too many questions, I hope someone has some answers. If you are a young evangelical in the United Church, I strongly encourage you not to leave. That does not mean staying will be easy. No group or point of view in this church has a monopoly on intolerance.
Some liberals can be every bit as narrow and exclusive as some conservatives can be.
One of the strengths of a broadly-based church such as ours should be that it has considerable room for diversity. This is one of the things that distinguishes us from churches founded on a narrow doctrinal basis, often in the conviction that they alone have understood the Gospel correctly. As to a curriculum for a confirmation class, it surely is important for people to be exposed to the beliefs and practices of other religions. We all share a planet that is not getting any bigger. Christian rock might not hurt either.