Hi EC
You've picked quieter months when finding accommodation shouldn't be difficult except perhaps during the holy week before Easter which next year (2018) falls in the last week of March. Generally the camino is flexible to cope with blips in demand and the quieter times you've picked should give you some headroom.
I think your plan is fine and you should stick to it, especially the Oct/Nov option and either route will work. The forum is prone to trending concerns about accommodation - what's reported here a few times doesn't necessarily reflect day-to-day life on the camino and can't really be taken as an accurate predictor of what the situation will be in 6 or 12 months' time.
As someone who has walked in high season a few times, when demand on accommodation is high, I'd still say, don't worry - in 99.9% of cases it all works out. And if for some reason (which you couldn't possibly anticipate now, 6-12 months before you leave), you arrive somewhere and there's nowhere to stay, the hospitalera/os will help you sort something out. And if that turns out to be a negative experience (actually quite often it can be a positive adventure) from there on in you can always start booking the places ahead of you.
I remember in late October on the first day out of Porto coming across a group of about 60 Portuguese pilgrims spread out along the path ahead of me and thinking gloomily that I wasn't going to find anywhere to stay that night or any night for the rest of the way to Santiago. But by the evening they'd all disappeared somewhere and I never saw them again.
Cheers, tom