Blastoise worth it?

No. Not only is it bad IV, that isn't a good moveset. Flash cannon is a worthless move.

That's the BEST defending moveset for Blastoise. Flash cannon will be cast repeatedly on defense.

If you are in an area with limited water types (i.e. there aren't Vaporeons everywhere) then maybe you could consider it. Even if there are a lot, but you don't have them, and want to save your lone Vaporeon to attack, you could consider powering it a bit to leave in gyms.

Overall though, Blastoise is just a weaker Vaporeon. There's no reason to power him up if you have better alternatives. Vaporeon and Slowbro will always largely outclass him. Overall I would recommend against the power up, but if you just like Blastoise / feel like you'd have more fun and be more effective with an added Water Type defender, then by all means go for it.

I like most of TTT's answer, but what level are you? How many candies do you have? Are they rare around you? If you are close to evolving a good squirtle you might want to do that.

Either way you are good to go man, you could evolve a 100 percent and get a moveset you hate. I'd say power it up decently if you like blastoise, but sadly a Vape will always outclass it for only 25 candy. At least blastoise is 10x cooler in my book. Good luck.

Nope

Dont power up, dust is hard to get, you will need it later for much better pokemons.