You seem to have provided a good overview of Sanctification already! I spent some time researching John Wesley and trying to uncover what he meant by Christian perfection in regards to sanctification. In general, Christian Sanctification has meant abiding more and more in the law (Dunning, Christian Perfection: Toward a New Paradigm, 157). Wesley, on the other hand, focused much more on growth towards a pure love (Wesley, A Plain Account of Christian Perfection, 3). Wesley's book A Plain Account of Christian Perfection would be a great place to start to read more specifically about he says.
In a sermon titled "Circumcision of the heart" Wesley describes Christian perfection as a habitual disposition to the things of God. In his book, A Plain Account of Christian Perfection, he emphasizes Christian perfection as purity of intention. Or when one's entire being, thoughts, words, and actions are all given over to God. The basis of such a commitment towards God is in love. Wesley says, "faith working or animated by love is all that God now requires of man," (Wesley, A Plain Account of Christian Perfection, 44).
Another aspect of Christian perfection, according to Wesley, is how one understands sin. Wesley states, "this is not sin, if love is the sole principle of action," (Wesley, A Plain Account of Christian Perfection). He explains a person can still make mistakes out of ignorance, but if love of God and neighbour is the sole driver of whatever a person does, then it is not sin. Just to balance Wesley out a bit, he also says this,
"there is no such perfection in this life, as implies either a dispensation from doing good, and attending all the ordinances of God, or a freedom from ignorance, mistake, temptation, and a thousand infirmities necessarily connected with flesh and blood." - in A Plain Account of Christian Perfection, 17.
I would highly encourage you to read A Plain Account of Christian Perfection by Wesley to gain a better more nuanced understanding of what he meant.
Christopher Bounds explores Christian perfection in the Church Fathers in his book The Doctrine of Christian Perfection. This would be another great resource to explore the topic a bit more.
A big part of the Biblical argument comes down to Matthew 5:48, "be perfect, therefore, as your heavenly Father is perfect." The word "perfect" in Greek is teleios. This word can be understood not simply as perfection, but as fulfilling the purpose to which you have been created (Borchert, "Matthew 5:48," 265). The argument is that the Greek word carries more of a dynamic understanding of growth, rather than perfection as a fixed state. Col 3:14, "And over all these virtues put on love, which binds them all together in perfect unity." Love is the binding virtue over all the others. Various other New Testament passages places an emphasis on love, not even to mention how Jesus places two commandments about love as the most important! Mark 12:30-31
"Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.' 31 The second is this: ‘Love your neighbour as yourself." There is no commandment greater than these.”
There is so much still to explore with Wesley's view of Christian perfection, what it means and what it doesn't mean. And I hope the above resources will be a helpful push in discovering more of what he read. Is he right? Now that is a bigger question which requires a whole new answer. But Wesley reorients sanctification around love, which does set him apart from other Protestant explorations of sanctification. I will close this answer with one final quote from Wesley,
"By perfection I mean the humble, gentle, patient love of God and man ruling all the tempers, words, and actions, the whole heart by the whole life. I do not include an impossibility of falling from it, either in part or in whole." - John Wesley (Rex Matthews, "Wesley's Perfection Reconsidered," 34).
P.S. if my formatting for sources is incorrect, I'm sorry. I tried to figure out how to use footnotes but couldn't find it.