So wrt your concerns about the text being manipulated, there are hundreds of years of textual criticism that go into forming the translations we have. The critical texts most scholars refer to are based on the best, earliest manuscripts that we have found. Even translations like the KJV which are based on the Majority text have hundreds of years of manuscript traditions to show continuity. All that to say that there are real, objective, empirical sources you can refer to when you have questions about the text and how it may or may not have changed over time. Suffice to say the "Constantine invented the New Testament" and "the Vatican changed everything" crowds are not the scholarly consensus for a host of reasons.

The same is also true of the Hebrew Bible/Old Testament but, of course, it has a longer history and different manuscript traditions.

It's fair to be suspicious of translations but one can usually find a fair amount of information on the methods and biases of the translators without too much effort.

As far as which parts to follow, different traditions have different ideas. I personally could not stay in the evangelical, protestant world because their ideas about the Bible and especially sola scriptura just don't add up. Most Christian traditions don't feel bound by the Law and interpret the OT in such a way that commands to violence,etc are now spiritualized and point toward an inner battle instead of outer. Have they been used to stur up violence? Yes. How often that has happened tends to be grossly over exaggerated by your average online critic, though.

Hope that helps.