Given that believing in your heart is faith I don't understand your question.
I have not read this thread- at all, so I have no context for your question. I was simply answering the OP's title question.
My question is how does one go from not believing to believing. How does a person get faith?
Is faith an innate property of man, and thus faith is a work of man being exercised to attain salvation, i.e. a directing of one's efforts, energies, works, thoughts, etc.
Or is faith a gift that is given to us from God, apart from ourselves?
The Protestant Reformers argued the second, that faith is a gift, and specifically that gift comes to us by God's word, as St. Paul will say in Romans 10:17, "Faith comes by hearing, and hearing by the word of Christ". Thus the word of God is effficacious, and through which the Holy Spirit gives us faith. And thus when Paul says "Whoever call on the name of the Lord shall be saved" he is not saying that salvation is conditional on the work to "call on the name of the Lord" but that the regenerated man, in faith, calls on the name of the Lord. It is from faith that we call upon and confess Christ our Lord.
The work is God's, to regenerate man by giving him faith.
It is not the work of man to meet certain conditions and overcome certain obstacles to attain salvation.
Sola Fide is the teaching that faith alone justifies not because faith is a thing I do to attain my own righteousness before God, but that it is the thing God gives me through which He imputes Christ's righteousness. Thus I, a sinner, am the passive recipient of God's saving work. My sins are forgiven because Christ suffered, bled, died, and rose again, and what He has done is mine because God gifts me His work, His righteousness.
It is a fundamental question of soteriology: Is our justification the work of God alone, or is it a joint effort between God and man working together?
-CryptoLutheran