How important are IV's to you?

I do the same with eevees.
Get a high level and with it's own candies, it is only 22 candy for the chance at a fighter.
You hit the jackpot...I know, I have one very similar.
It is a beast to use, and fun too.

I would not invest anything else into it, it has already paid off. Use it as it is and you will get a better one eventually with that moveset - until then, let them all burn.

Try it out, you have nothing to lose by using it.

Sidenote - rips serious damage on a big Blissey very fast, so that is always good. It may go down...but so will the Blissey if you have something else to finish the job.

IV is important if you plan in using stardust on it, if not doesnt matter, if it has good moveset keep it and use it

Do what makes you happy, that's how I play the game, just out working yesterday. Yes, IV's are important to me. Flareon OSxOH is best fire attacker at the moment. Typlo is very good as well, you got the second best set for him.

Per power up, again, do what makes your happy -- me, I'd wait, Eevee's are not hard to come by, sooner or later you'll get that set again.

That Flareon doesn't need power ups to perform well, and the difference in DPS between a 50% and a 100% isn't as big as people expect.
Keep that beast and use it!

As a general note, I am a big fan of catching high CP mon and just using them as is. IV is not as important for attackers because A.) You are not fighting for a gym spot (higher IV=higher max CP potential) and B.) You have complete control over dodging and C.) You get to save a ton of dust. The worst is when you catch something rare/powerful like a t-rex and his IV is 64 (decent) but his CP is like 125 and then all your friends make fun of you for having a useless t-rex….not that I would know or anything…..