Charizard Question: Do I power up the ultimate Charizard Defender?

Waterlooyo,
Sounds like you have a plan.
You can choose to play the way you want.
Charizard will not go to high cp, and would not be able to sit in a gym near where I live, so I would not power up a defensive Charizard.
But if that works for you and makes you happy then do it.

I honestly think it doesn't matter if you have 5 lapras' and 5 snorlax in your gyms. most people use them because they have high cp, thereby deterring a lot of low level trainers and moving you to the top of the totem pole. Strong trainers won't care though. also, you can hold more than 10 gyms - you just aren't able to collect for all of them.

IMO i would pump up the 91IV, since he is almost there. But seeing as you having a plethora of dust and candy, you could go nuts with it.

I wouldn't power any of them up. Cahrizard looks cool and seems underpowered. That being said, he's just okay. There are better mons to do what he does other than look cool. Save the candy and evolve more charmanders. XP is worth more (through charmander evolutions) than powering any of those charizards up.

If you love Charizard then go for it. But sadly whatever the move set it won't be a good defender. Same for all fire mons and Rhydon.

With the amount of dust you've got I'd go for it. He's not going to be a great defender (but there are worse), he'll add interest for attackers and will look cool. Try and place him between two water defenders to force a change of attackers to maximise his usefulness.

I'm so bummed Blastoise's max CP is so low. I've stuck to powering mines up and I'll max him out, but in your case might as well. Just power up the one you like best as an attacker. While he's a mediocre defender he's an amazing attacker still. WA+ anything is great.