I have a small gap in my reading/study/writing schedule, so I've decided to slot 2 Thessalonians in. I'm planning to cover the whole book in three posts, hopefully all before the end of the year.
You can read the text here.
Paul  opens his second letter to the Thessalonians with a wish of grace before going into his customary thanksgiving section. He has much to be thankful for. The Thessalonians are growing, especially in their love for one another and their faith/faithfulness/fidelity. Standing firm in their commitment was not easy given the persecution they faced. They are a church in need of encouragement, so Paul affirms them, essentially calling their witness exemplary.
Next, Paul goes on to offer further encouragement, here offering hope for a beleaguered church in the final judgment. There are a couple of points of emphasis. First is that the judgment of God is just, or in keeping with people's deeds. Those who persecuted the Thessalonians would receive appropriate condemnation from Jesus on the last day because of their opposition to him. Second we need to remember that this reminder is given by Paul to help them to stand firm in their faithfulness. Steadfastness through persecution prepares them for salvation and gives them an opportunity to demonstrate costly loyalty to God. In exchange, God will avenge them on the last day, and they just needed to stay on course.
This section concludes with Paul moving into a description of his constant prayer for the Thessalonians. He wants them to remain faithful to the end so that they are rewarded by God for their fidelity, and to that end he prays for God to continue to bestow the grace needed to sustain them. What does God get out of this arrangement? Glory, as the Thessalonians honor him with their lives.
 I feel reasonably confident that Paul wrote 2 Thessalonians. See, e.g., the extended discussion in Malherbe.
 I think it's hard to know what exact nuance is intended here, but I typically prefer fidelity (a concept which encompasses faith and faithfulness) unless there is a clear reason to limit the scope to on or the other. In vs. 3, Fee and Gaventa leans towards 'faithfulness' while Malherbe opts for 'faith.' Given the inclusio formed by vs. 11 I prefer either faithfulness or fidelity. I lean towards the latter especially given the emphasis on steadfastness in the following verse and the rest of the chapter.
 I think the challenge for any Pauline interpreter is to stick to his points of emphasis and try not to develop his thought beyond that.
 Fee makes clear that the emphasis is not on God as avenger as it is on the judged getting their due. As for the nature of the judgment to say much more than it is catastrophic and a complete separation from God is reading too much into the text. It could fit either annihilation or eternal conscious punishment depending on what one brings to the text or emphasizes within it. I would issue similar warnings about those who completely generalize vs. 8. The goal of this text is too specific to warrant a broad generalization here. In intense passages rhetorical overplays to make a point are common.
 Judgment according to works is at play again here.