First let me say that you have done about as well with these questions as I have seen. Thank you. Further, as I stated, I am not a calvinist in all thought. I think great arguments for God's total sovereignty AND man's free will choice can be made from Scripture.
BUT.... there are some issues with your analysis. Here is the Romans passage with a little more context.
Romans 12 New King James Version (NKJV)
Living Sacrifices to God
12 I beseech[
a] you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God,
which is your [
b]reasonable service. 2 And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what
is that good and acceptable and perfect will of God.
Serve God with Spiritual Gifts
3 For I say, through the grace given to me, to everyone who is among you, not to think
of himself more highly than he ought to think, but to think soberly, as God has dealt to each one a measure of faith. 4 For as we have many members in one body, but all the members do not have the same function, 5 so we,
being many, are one body in Christ, and individually members of one another.
Note that Paul is addressing BRETHREN. I think when reading this passage it is reasonable to say that the measure of faith given to each one is meant for the MEMBERS IN THE BODY OF CHRIST, not everyone.