Fritz,
What a journey you are planning! To walk from Santiago to Rome in winter should be quite an undertaking.
As for problematic spots
going eastward from Santiago in addition to those that you have identified might be from Santo Domingo de la Calzada to Najera or across the Montes de Oca to Villafranca Montes de Oca as well as from Ponferrada to Rabanal de Camino via Foncebadon. Any place can be dangerous in fog, heavy rain or, of course, snow.
Many albergues and regular tourist accommodations will be closed, but there always is someplace open. Read the handy list of open
Winter Albergues which can be downloaded from the Resource section of the Forum.
However do plan to carry some food
always will you. For many summer-only shops and bar/restos will be closed. Hence my food basics include tea bags, packets which make a cup of soup (even including croutons), firm cheese, small sausage, simple cookies and some chocolate. Nothing heavy but enough to exist for 24 hours if need be. On past caminos especially during storms when I stopped in small and remote albergues far from any supply source novice pilgrims have often staggered in wet, cold and hungry. They may have had the best gear but carried no food.
Sillydoll who is a Forum member has compiled encyclopedic information on
Winter Walking. Other good accounts of winter walking by a Forum member Kialoa3 are
his 2010 and later blogs . Be sure to read what others and I have written about walking in winter in this earlier
Forum thread and in this thread comparing
summer and winter expenses.
Winter is a great time to walk, but you must be prepared!
Happy preparation and Buen camino!
Margaret Meredith