1-4. The calling refers back to chap. 2 and what precedes, only enlarged by chapter 3. The unity of the Spirit is the realization, in walk down here by the power of the Spirit and in spiritual life, of the unity they have in Christ. The body is one and cannot but be; it gives character to the unity but is not it.
9. κατῶτερα does not mean anything particular but what is below, the apparent earth in contrast with above all heavens, so as to fill all things. It naturally suggests Hades, which gives no definite idea, and is not meant to do so.
12. πρός is the proper object and purpose first in the apostle's mind, but then use reaches out to the secondary more collective ones.
13. The whole is Christ being fully formed in us and we after Him in soul, according to the revelation that has been made of Him, my soul formed into all revealed of Him.
22-24. The truth as it is in Jesus is the having put off and having put on; the renewing is constant, hence ἀνανεοῦσθαι, in Colossians ἀωακαιωούμενον and in knowledge.