Like Thomas says, it is quite hard to advise, but if you are walking about 14kms now on walks, I'd be inclined to keep your first few days to about the same. I had Montbonnet and Monistrol d'Allier for my first two nights both times, and found it was a good way to walk myself in. I struck bad weather on Day 1 both times, several kilometres before Montbonnet- first time with sleet/snow, and last year with a severe hailstorm, so I was glad to be stopping at Montbonnet to get my wet cold clothes off! The climb down from Rochegude on Day 2 was quite tricky for me with my short legs, and the climb up from Monistrol d'Allier was quite long and steep in places. My first time I walked only as far as Saugues on Day 3, which was perhaps too short, but last year I walked onto La Clauze. By the time you have walked two days to perhaps Monistrol d'Allier, you will have more idea about how far you can walk per day.
Your option C was what I did my first time. Personally, I wouldn't stop at St-Christophe, unless you are leaving Le Puy later in the day for some reason (eg sightseeing there, which is always a possibility.)
All the best with your plans,
Margaret