Congratulations MA on your Bible reading! That is a monumental task that takes much discipline!
I agree with Malohaut 99%!!

I think he meant to say that we are to baptize in the name of the Father, Son, and Holy Ghost. Matthew 28:19 We pray in Jesus name because it is His death, burial, and resurrection that makes it possible to approach the Father's throne.
The Bible says that we now see through a glass darkly, but then we will see face to face. Our God is exciting! He and the things of Him are mysterious and make us seek after Him. I don't think we will ever, not throughout eternity, exhaust finding new and wonderful things about Him to add to that which we already know. We will always be discovering new nuggets in the Bible! Yet, here on earth, our understanding is limited. The same faith it takes for salvation, it takes to believe the Trinity exists, just as the Bible says it does. That is where our knowledge stops. God has given us what is important for us to know. And do not forget, straight from the Garden of Eden, the enemy has not changed...he wants to shed doubt on God's Word!
In the last verses of Ephesians speaking of the body of Christ and marriage is intermingled. God says:
This is a great mystery: but I speak concerning Christ and the church. vs. 32
He knew that it would be difficult to comprehend. Is it not just as difficult to understand that when we are married, we are literally one flesh with our spouse? Because of the Ephesians verses, I believe that the marriage should be a picture of the Heavenly Kingdom and how it functions, it's order, if you will, and it explains the Godhead. I once read in these posts, and firmly believe, Heavenly things will not completely be understood until we reach Heaven. He will have more senses, we will see things 100% Spiritually then. Streets of gold, but see-through, like glass? Unimaginable!
For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three agree in one. I John 5:7
I do not fully comprehend it. I have come to the same conclusions as Malohaut. The Word says it, it is true!
Thaddius, the Bible tells us to judge ourselves that we be not judged. The helmet of Salvation tells us that we are saved. We know how to be saved. We can probably remember the day that we are saved. We can figuratively take a stake and drive it into that day! We trusted the LORD and asked Him into our hearts. That settles it! Those that will say, "Lord, Lord!" Are doing works to gain salvation. They are not trusting in Jesus for salvation, but in their good works.
The only thing that we can do is take Jesus at His Word. If we have done the steps of salvation, (my signature has them for those who may not know), we are saved! Once saved, we will show the fruit explained in Galatians 6:22~23. Notice it is the "fruit" all those things will be manifest. I think those grow, ripen, and will not reach full maturity until we see Jesus face to face. In addition, the Bible tells us
Beloved, let us love one another: for love is of God; and every one that loveth is born of God, and knoweth God.
He that loveth not, knoweth not God; for God is love. I John 4:7~8
How do we know if we are Christians? We are Spiritually able to show forth unconditional love. Just like Jesus did at the Cross...forgiving and turning the other cheek has not one ounce of flesh attached to it, that is God in us! The verses in Matthew you mentioned follow Jesus telling us that we can know them by their fruit, and are preceded by Him telling us that we are to live it, not simply hear it. Basically, I think it is saying we can know how to be saved, but unless we have accepted Jesus for ourselves and have a relationship with Him, that knowledge is worthless. The good things that we do, while we should live for Christ, and makes us like the man who lived upon the rock, vs.24~25...our good works could never get us to Heaven.
I hope that helps. I don't think there is a single Christian that has not been in the spot of questioning their salvation and shuddered at the fact that some will not be in Heaven that thought they would. Jesus, as you already know and have accepted, I feel certain, Thaddius, is the only answer.
Jesus is the way.
Jesus is the truth.
Jesus is the life.
No man can come to the Father, but by Him.