That looks almost how I do my planning on longer trips!
With my short trips it has been get a FP+ for whatever day I can and then take a 15 minute break, regroup and plan backwards!
I might suggest you try for the FOP on the 29th first before the 31st. The 31st is much more likely to have open availability since it's your 7th day (unless Halloween has big effects that I don't know about since I've never been at WDW on 10/31). And the 27th is not very likely since it's your 3rd day - so that would still stay 3rd.
I saw someone report on the YC/BC thread today, their fastpass day, that the first FP+ available for FOP was in the evening of their 5th day, 6th day had more availability.