Thanks for your interesting observations about growing on an Umbrian hill. The wind sounds daunting. In midwinter, even at your latitude, there is a lull when light falls below a certain level, in your case for much of December and January, but mild temperatures can offset this to some extent.
When mulching initially to smother thick weeds or grass, I prefer cardboard on top so that it rots less quickly, compared to when it is buroed by moist compost and then loses the mulching effect. On the other hand, keeping it in place is tricky, I use some stones on overlapping edges, but in high winds this may not be enough. You may do better to use a double layer of cardboard and some organic matter on top.
Grafted plants are, I think, not worth the cost. I am doing a comparison of tomatoes here and currently there is actually more fruit on my home raised non-grafted ones, although the grafted plants’ leaves look healthier.