Varda&Melkor and Marriages of Valar

[Raynor]

I wonder if he did this to 'Christianise' the text or to remove sub-creation of 'beings' from the capacity/remit of the Valar?

I would say the later; in the Christian tradition, there is the interpretation that the refference "the sons of God" found in Genesis 6:1-4 (who mated with Men and had children with them) were in fact angels, which would imply that they had bodies (as possibly stated in Mark 16:5) and reproductive capacity - which is unlike the 'angelic' beings of Tolkien, as he later conceived them in Annals of Aman:

Note that 'spouse' meant only an 'association'. The Valar had no bodies, but could assume shapes. After the coming of the Eldar they most often used shapes of 'human' form, though taller (not gigantic) and more magnificent.