Flareon

Flareon in general isn't a great PvP pick. Its stats favor attack over bulk, all of its attacks are the same type making it easy to trap, and fire has some easily exploitable weaknesses. Ember and Heat Wave are bad moves all around; Ember is the compromise between Fire Fang's increased damage per turn and Fire Spin's energy per turn, and Heat Wave only deals 95 damage for 75 energy. In gyms/raids both of these moves are strictly outclassed by Fire Spin and Overheat.

The only thing going for those moves is that they're legacy, meaning if you change them you can't change back to them. Some people collect these and would say it's a nice trophy to have. If you're dead set on using a Flareon I'd rather get one with better moves.

Nope.

Id keep it as is, fire isnt that much of a relevant type for offense, the tier 4 and 5 raids arent weak to it, and theres other options that are better like moltres and blast burn Charizard if you have them. Keeping the fareon as is, while not the best, is a legacy holder, meaning you cant get those moves back. I Tm's a lucky double dragon dragonite (DB/DP to DB/OR and I regret it, mostly for collection purposes, but also because if I waited a week, i'd have found out about the second move)

As for use of fire types, I have a high level sky attack moltres eith overheat a s a second move, and several blast burn Charizard than I rarely use, last time was registeel for the Charizard and, well, not yet for overheat with moltres.