3:1 The word for give (didoo-mi) as in "love the Father has given us" is in the perfect, suggesting an act in the past (Jesus) that still has a present effect (being called the children of God)
Also interesting is that the hina clause that governs the phrase "called children of God" is not connected with the phrase "and we are" The Greek reveals this is from a different thought (as indicated by the verb "we are" being in the indicative and not subjunctive mood as "called" is). Does this mean that we are children of God regardless of the love on the cross but that in the cross we may be called children of the father??
3.2 The word "kathoos" (just as) appears in this section three times -- just as he is; just as he is pure; just as he is righteous. Although the overall logic may seem to imply "works-righteousness" in this passage, it is helpful to keep in mind that the ground for all of this is Christ and his status. Indeed, the transformation comes when we see Christ, which cannot happen until he appears. I am not saying that this passage fits into Lutheran mechanics nicely, but that still, the primary actor here is God.
3.3 Moreover, the tenses about what we will be in 3.2 are in the future; and now in 3.3 we come to the idea of hope, expressing the thought that God is not done working on us! Indeed, even the verb tense for purify is a present tense -- that hagniz-oo (to purify) is an on-going reality, not a one-time event. So, over and against a simple message of "Christians are fully realized saints and not sinners in any way," this passage points toward the work still to be done.
3.6 A key word in Johannine thinking is "men-oo" which means to abide (abide in me as I abide in the father...") This is the verb here.