So I want to exit the flue about 8' off the ground through the gable end. My thinking is if it's forced out it will push it further away from the house.
I cant see that working very well.
The power of the external wind / air movements will be larger than any fan you can fit. Plus the actual amount of exhausted flue gasses will be limited by the air in setting on the stove. Open that up & the stove will over fire with the extra air flow.
Plus building regs give minimum distances from windows / walls / roof pitches.