A - Thanks for the question. God bless you in your struggles. There are several other questions that are a part of your struggles.
*How is it possible that Christ is present to us under the appearance of bread and wine?
Nobody knows. This is part of the mystery of God. He doesn't fill in all the details. We also don't know most other things about how God acts. How did God create something from nothing? How did God become man? How did God guide the human authors of Scripture to write the truth? How did God perform miracles? We just don't know.
*Why does God become present to us through the appearance of bread and wine?
Because just as our bodies need food and drink, so our souls need nourishment from God - his grace. We receive grace in many different ways, but the system that Christ established for us to primarily receive it is through the Sacraments. It binds us to Christ. St. Cyril of Alexandria said,
As two pieces of wax fused together make one, so he who receives Holy Communion is so united with Christ that Christ is in him and he is in Christ.It is the primary way Christ draws us to Himself. This is the same thing that Christ tells us in John 6:
Whoever eats my flesh and drinks my blood remains in me and I in him. - John 6:56The early Church saw the Eucharist as literally the body and blood of Christ that draws us to Jesus and unites us to the Father.
"I have no taste for corruptible food nor for the pleasures of this life. I desire the bread of God, which is the flesh of Jesus Christ, who was of the seed of David; and for drink I desire his blood, which is love incorruptible"- Ignatius of Antioch (110 AD).The witness of the Church fathers is unanimous. Not until the reformation was there doubt about the Eucharist and the reformers (e.g., Luther, Calvin, Zwingli, etc.) almost were unanimous in having some kind of spiritual presence at the very least. So, the real rejection of Christ's presence in the Eucharist is even more modern than the Reformation. It comes from the Anabaptist tradition and entered into Evangelical thought in the USA. Several questions then arise:
"They abstain from the Eucharist and from prayer because they do not confess that the Eucharist is the flesh of our Savior Jesus Christ, flesh which suffered for our sins and which that Father, in his goodness, raised up again. They who deny the gift of God are perishing in their disputes"- Ignatius of Antioch (110 AD).
"For not as common bread nor common drink do we receive these; but since Jesus Christ our Savior was made incarnate by the word of God and had both flesh and blood for our salvation, so too, as we have been taught, the food which has been made into the Eucharist by the Eucharistic prayer set down by him, and by the change of which our blood and flesh is nurtured, is both the flesh and the blood of that incarnated Jesus" - Justin Martyr(148 AD)
"If the Lord were from other than the Father, how could he rightly take bread, which is of the same creation as our own, and confess it to be his body and affirm that the mixture in the cup is his blood?" - Iraneus (148 AD)
"'Eat my flesh,' [Jesus] says, 'and drink my blood.' The Lord supplies us with these intimate nutrients. He delivers over his flesh and pours out his blood, and nothing is lacking for the growth of his children" - Clement of Alexandria (202 AD)
"The bread and the wine of the Eucharist before the holy invocation of the adorable Trinity were simple bread and wine, but the invocation having been made, the bread becomes the body of Christ and the wine the blood of Christ" - Cyril of Jerusalem (350 AD)
-By what authority is the clear biblical evidence, the unanimity of the church and history tossed aside?
-What is so important about a mere symbol?
Not everything is supposed to be seen with mere reason. God becoming man is not irrational - it is above reason. The same with the Eucharist. If you still think it is so, then I recommend you read the following books and then ask if you still see it the same way:
-The Lamb's Supper by Scott Hahn.
-A Key to the Doctrine of the Eucharist by Vonier.
-The Hidden Manna by O'Connor
I would also recommend you talk to someone on staff and in person about your struggles. There is no pressure for you to believe, but we want to make sure you have the truth about the situation to help you.
As for your standing in the Church - you are certainly still Catholic and in your wrestling with these issues, we will keep praying for you. Faith isn't necessarily supposed to come easily. If you were to come to a final decision that the Eucharist isn't what the Catholic Church teaches that would effect your standing of full communion with the Church, though you would still be a Catholic.