The baptism in the Holy Spirit has been going on since Acts 2 for Christians, and a bit earlier if you count Christ. It is one of the divisive issues of the church today, but that doesn't make it less real. Since I have witnessed both baptisms in the Holy Spirit, seen the evidence of changed lives, and have seen the gifts of the Spirit in action, the issue isn't an elaborate construct for me or the Christians I know.
The trinity is clearly present throughout the Old and New Testament.
These are literal Bible truths.
You are correct that Christians today do use terms which are not found in scripture - word for word. We use terms like rapture to describe the events as written in 1 Thess. 4, 2 Thess. 2, and Revelation 4:1 (hereafter being after the church age of Rev 1-3). It is easier to just use one word that is understood among believers than to read out 1 Th. 4 every time you want to talk about the event.
You are right that people who have not heard the truth wouldn't need to hear these things, but if you have been brought up in a Christian household and have chosen to reject Him, you really aren't in that camp.
I won't argue that the church of today has gotten away from what Christ wanted it to be. He tried to make it clear that the church needed to stay united, and every fracture, brought about by sin has fractured the church and weakened it.
Denominations are a curse. But so is the sin in the church that led to some of those splits. Protestantism started because Luther couldn't stand what was going on in the Catholic church and he couldn't find a way to fix it from within. Was he right or wrong? God will decide that.
I can say that the Spirit filled denominations are on the rise and the more classic denominations are failing. The evangelical denominations have had their issues and failures as well because people aren't perfect. You can stand on the outside and throw stones or stand on the inside and try to change things for the better. God wants change first in His children's hearts and then in His church and then in the world outside the church.
You've mentioned LGBT issues a few times. I would agree that Christ would be out trying to save the lost. And once they had accepted His salvation, He would have been telling them to go and sin no more, just like the woman taken in adultery. Preaching against sin is never popular. If you believe people are destined to end up in hell, how is trying to keep that from happening by any means possible wrong? You should love the people and do good whenever possible, But you should also preach the truth in season and out of season.
This Sunday is Pentecost Sunday. It is the celebration of when the Holy Spirit was poured out on the believers in the upper room - the first of many examples in the New Testament. Of one thing I am certain - when the Holy Spirit is in control of God's church, things work fine. When He isn't, there are problems.