but I was an evangelical Christian for years

Key word: evangelical

There is a wide, large group of Christianity that is not 'evangelical' or American in origin or nature. What you experienced is a narrow, cultural ghetto of Christianity. While I fully understand the pain and stupidity you've experienced (also raised conservative evangelical), I've explored and found a nice home within progressive Christianity.

The only mistake I see you making is holding onto something we were both taught, like all good conservative evangelicals - that the Bible is literal truth and all of it is equally valid. My friend, that simply isn't true. And I back that up with thousands of years of church history that speaks that truth, the same history that is actively suppressed and ignored in conservative evangelicalism.

So, to your specific points/questions.

If you reject the teachings of Paul, why not reject the entire Bible? How do you decide what parts to continue to follow?

So, if I reject one influential theologian's work, I can't be a faithful Christians? That's absurd. By the same logic, you can't be part of any movement or group unless you agree with every person within it. This is fundamentalist thinking at it's core, which I reject.

How do you decide what parts to continue to follow?

I believe and adhere to the commands that were spoken to me. The writings of an angry pastor about homosexuality in Rome being a result of idol worship don't pertain to me. I'm not Roman, people don't worship physical idols by having sex in front of them in my society, and we view sexuality differently in 21st century America.

Why not just be an atheist humanist at that point?

Because Jesus' words, ministry, and the Gospel are addressed to me. Paul never intended for his letters to be used as theology for the whole church, merely the Roman church. Christ's words were addressed to all people.

They won’t be convinced that Pence’s values are not the values of Christians.

That's because conservative evangelicals know it's a sham. That's why they've decided to grab onto political power to try and transform laws, rather than grab onto transformative power and transform their communities. Every conservative evangelical I know is disconnected from church life/spirituality, votes like a wacko, and is more likely to believe in government conspiracy theories than the Power of the Holy Spirit.

So yea, that's a lot of fucking words.