the Church itself is the final authority in all matters of faith and practice since it must define and interpret Scripture and Tradition.
With that one statement, he undermines his later claim that the sola scriptura position makes the Scripture the final authority in all matters of faith and practice. Why? Because if the Scripture's needing to be interpreted by the Church makes the Church the final authority, then the Scripture's needing to be interpreted by the individual Protestant makes the individual Protestant interpreter of Scripture his own final authority. And that conclusion is not compatible with Michael's claim that sola scriptura makes the Scripture the final authority.
One option for Michael, while retaining his position in the quotation cited above, is an ad hoc move: to claim that if the Church interprets Scripture, then the Church is the final authority, but if the individual interprets Scripture, then the individual is not the final authority. The problem with that position is that it is, ad hoc. The other option for Michael, while retaining his position in the quotation above, is to bite the bullet and grant that each Protestant is his own final authority, basically his own pope. The problem with that option is that it contradicts his claim that Scripture is the final authority. The third option, of course, [and the correct one] is either to abandon the argument he makes in the quotation above, or make a distinction between the two senses of 'final', as I explain below.
The mistake in Michael's argument is the univocal conception of "final". He assumes implicitly that final in the order of determination is final [i.e. highest] in the order of intrinsic authority. That would lead to reasoning such as this: if the Church is the buck-stopping point in the determination of what is orthodoxy and what is heresy, then the Church has more intrinsic authority than the Word of God. But nothing can have more authority than the Word of God. Therefore, the Church isn't the buck-stopping point in the determination of what is orthodoxy and what is heresy. Such a perspective fails to see the possibility of the Magisterium being the servant of the Word of God (CCC 86), and having the authoritative interpretation of Scripture and the authoritative determination of what is orthodoxy and what is heresy. It fails to conceive of the possibility of authoritative hierarchy.
If we applied this way of thinking to the relation between the Father, the Son, and ourselves, it would mean that Jesus can't be the interpreter to us of what the Father is saying, without making Jesus the authority over the Father. But that is clearly false. Being the "authority of" is not the same thing as being the "authority over". Jesus is the authority to us concerning what the Father is saying. But Jesus is not an authority over the Father; He is an authority under the Father (see here), while being homoousious with the Father. Likewise, the Church is not greater in authority than the Word of God written in the Scriptures, but the Church is the authority to us *of* the meaning of the Scriptures, and of what is orthodox and what is heresy. Final in the order of authoritative determination is not the same as final in the order of intrinsic authority. Michael's argument fails to take note of that distinction, and thus creates [for his own position] the dilemma of being either ad hoc or contradictory [i.e. claiming that Scripture is the final authority but also entailing that each individual interpreter is his own final authority].
Lord Jesus, please help Protestants and Catholics better understand each other, and be reconciled in true unity. In the name of the Father, and of the Son, and of the Holy Spirit. Amen.