I agree there are many different views about biblical texts. I belonged to Churches that taught all three of those beliefs you cited.
Our salvation belongs on our having a personal relationship with God thru his son Jesus and recognizing that Jesus is our only savior. John 17:3 states our everlasting life depends on our knowing God and his son Christ Jesus and this "knowing" denotes we should know them as we would know a personal friend. That is why we are baptized in the name of the father, son and holy spirit. Not into an organization like the Witnesss do. So that we are united with them by Holy Spirit and have a personal relationship with them. If we have a personal relationship with them, they will teach us with holy spirit what we have to learn as individuals. but still as individuals we will be on different levels spiritually. Some will not be able to fully understand the deeper teachings. But I don't think the trinity or nature of holy spirit is really an important issue as far as our salvation goes although some churches tell you it is, and I will tell you why I feel this way
For one thing nothing is stated in the bible that says we have to understand the nature of the Holy Spirit to be saved. Jesus even showed that it was a hard teaching to understand when he compared the spirit to the wind for Nicodemus. Nicodemus still did not understand what Jesus was saying. He used wind as an illustration as no one had seen holy spirit before that time. Nowhere did Christ say unless we full understood the nature of holy spirit and taught it the proper way that we will not be saved. It is an an issue essential to our salvation.
Another reason is that Christ said people would know his true disciples by their love they had among themselves, not by their knowlege of or understanding of every scripture. If we are united in love for all our brethren, we are disciples of his. Now of course we have to agree with the basic teachings of the faith which the NT shows are simply that we need to recognize that Christ was the son of God, he gave his life a ransom for us, died for our sins and was resurrected on the third day. Any who say Jesus was not the son of God, or did not die for us or was not resurrected back to heaven, if they claim to be in the body of Christ, would be heretics.
Also to show it was not head knowledge or being able to interpret all scripture that Christ found important for his followers but rather how well we know him is this scripture:
Here Jesus says to the Pharisees, "You diligently study the Scriptures because you think that by them you possess eternal life. These are the Scriptures that testify about me, yet you refuse to come to me to have life
So, although the Pharisees knew the scriptures backwards and forward they did not know Christ in an intimate way. If they did they would have known that showing love and mercy were far more important than interpreting or recalling scripture.
Even though some do not agree with interpretations of certain scripture, if they agree with the few you had to in order to join the faith - love will cover them for the things they still do not understand. And those Christians who are more mature in the faith need to try to help those who are babes to learn the deeper things. We are never to berate them or judge them though. Our helping them should be in a loving way. And I also believe a time will come when all Christians will be united in the faith and have accurate knowlege of all scripture together. But, Jesus himself will accomplish this not a made made religion of our day.
If we are in the body of Christ and have the Holy Spirit within us we will follow Christs footsteps and teach to the best of our ability based on what he taught us thru the Bible. Of course the basics should be understood and some religions like the WT do not even understand the basics. But there is a lot of freedom in Christ and many things are not black and white and we have the freedom of convincing ourselves what we hold to be true. To believe we have to agree on everything is not a biblical teaching at all. I see no reason why I cannot enjoy fellowship with other believers in Christ just because they may believe other doctrine of their church that I do not believe in.
One thing I hate about some religious organizations is that they do not allow questioning of any sort. This is not a bible teaching as the Bereans were called noble minded Christians when they checked every teaching that the Apostle Paul gave them. If they disagreed with some things that would have been o.k. as they needed to be convinced in their own minds.
Most of the mainstream religions today including the Catholic and Protestants among others do agree with the basic doctrines and that is why we should consider them our brothers in the faith.The seperation comes from the doctrines the churches teach that are unique to them, not because they are not in agreement that Christ is our only savior. If not for these institutions - we would always consider all Christians our brothers.
It is o.k. as a Christian to say we don't fully understand everything. And it is o.k. to disagree on matters that are not important to our salvation. We need to stive for spiritual harmony not comformity.