Diakonos; deacon, or deaconess; the word 'minister' here connects with 'to minister' and 'ministry' elsewhere, as ch. 15.31. She did the needed service in the assembly there; she was not properly a servant.
'Assist' is 'to stand by her and help her.' 'Helper,' prostatis, in this verse is stronger and has a higher sense, and means 'helping as a patron. ' It was used for a Roman patron, and is applied in special honour to Phoebe as one whose help many had been dependent on and had profited by. It was a complimentary touch of heart in which the apostle never fails: they were to 'stand by her for assistance,' but she had been 'a patron' in the matter.
As Luke 9.39, 'crushing;' Rev. 2.27; 'broken in pieces.'
It formed no part of what was unfolded in the ages of time, in which God developed his plans in creation; it was a purpose before, and eternally hidden; it was not in reckoned time. See 1Cor. 2.7-10; Eph. 3.2-11; 5.32; Col. 1.25-27; 2.2,3.
The natural construction would be 'to him.' These breaks, through long parentheses, are common with Paul.