Flareon: iv or moveset?

If I were you, I would not powering it up. Flareon is a very good attack pokemon. However it has a huge flaws : He has a bad defense and its stamina is really too low.
Besides, Heat wave isn't worth fire blast at all. If you use your flaeron while attacking Eggsecutor , It will be destroyed while he is charging its heat wave and it won't be as strong as fire blast .
My advice : Wait for a Arcanin OR wait for an update in the game which will allow you to change some attacks (I'm sure it will happen someday). In the meantime, keep it on the side. but Don't transfer it.

not necessary, it can take down 2000 cp above grass defender without big problem, save it as a gym trainer

Considering how ez it is to get flareon I would wait for one with Fireblast even if the IVs aren't as good (still above %80 tho)