I believe anybody who knows Jesus Christ is their Savior is a Christian.

One has to be born again, born of the Spirit. God gave us His Holy spirit to house & dwell within as a part of Him to guide us...etc, without that we are not fully IN the spirit or ABLE to know or even comprehend. That is what helps align our will with God, open our hearts & eyes- in the receptiveness, open to Him. (It is more than a simple acceptance too, it is one that will permeate. That is not just my words, it is scriptural.) Those who have chosen to have Jesus has their Savior, should abide in the spirit and the Spirit of Truth that abides IN Him-also., they go together.

Yes, that is one of the most important parts of the faith imo

No, considering it is not even part of the Bible. It was something that was invented by a Catholic Priest years later.

^in what way isn't it in the bible?

The only reason I picked "no" is because there's no "Unsure" option. Honestly, you really shouldn't force people to fit into your "black and white" mindset. Decision making isn't that easy for a lot of people.

*4 months later*

My answer is: The Trinity is a Christian concept (at least to my knowledge) and I don't see myself as a Christian anymore. I'm a Deist.