Such is the confidence refers to the claims that Paul makes about the Corinthians in verses 2 and 3. Revised English Bible says “It is in full reliance upon God, through Christ, that we make such claims.” And Barclay, changing the order of the propositions, has “we can make such a claim because of our confidence in God through Christ.”

We in this verse does not include the readers. Likewise in verses 5-6, the plural pronouns probably do not include the readers. Some interpreters understand that Paul is referring to himself by means of the plural pronoun, and they translate these pronouns with the first person singular pronouns, “I,” “myself,” “my” (so Moffatt, An American Translation, and Parola Del Signore: La Bibbia in Lingua Corrente).

Through Christ toward God: it is through his relationship with Christ that Paul has confidence toward God. These last two words may indicate where Paul places his confidence (“in God” Good News Translation) or may indicate that his confidence is expressed in the presence of God (“before God” Barrett). If the latter is the correct understanding, then toward God here is the same as “in the sight of God” in 2.17. New Jerusalem Bible says “through Christ in facing God.” And New International Version gives essentially the same meaning with “through Christ before God.” Translators choosing this option may find it more natural to say “… in the eyes of God.”

Quoted with permission from Omanson, Roger L. and Ellingworth, Paul. A Handbook on Paul’s Second Letter to the Corinthians. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .