The reading here is perplexing, but it is either as translated, or 'our brother and minister of God.'
Or 'we are to be,' that is, such is the lot of Christians; but 'told you beforehand' seems to make it applicable to the Thessalonians. I suspect both were in the apostle's mind; but it is added to ver. 3, and not the repetition of it.
Or 'have good remembrance of us, always desiring much to see.'
Epi with a dative. Here, and in 2Cor. 7.7, the apostle states what gave occasion for comfort to him -- the circumstance, not the cause. It is a similar construction in ver. 9: 'for all the joy.' We can say 'for' perhaps there, but it is the occasion of his thanksgiving; his thanksgiving was conditional; that was necessary to it as a condition precedent.
The one article in Greek refers 'God and Father' to one person, without necessarily referring 'our' to more than Father, which it follows in Greek. 'Now may himself [who is] God and our Father.'
Here 'direct' in Greek is in the singular; God the Father and Christ the Lord forming, so to speak, one in the apostle's mind, though, personally, clearly distinguished.
'You' is in contrast with 'our ... to you.'