This is much closer to being balanced, but it also feels wrong. Maybe it's from using flamethrower too much before, or maybe it's that people hardly ever used flamethrower on me, but right now it feels wrong somehow.
My initial desire was for low damage and easy fire stacking.
The damage right now is probably pretty good. I think you could argue in either direction, but if I were to choose one I would say it is a smidge on the low side (by like .1 per particle or so).
But the fire stacks feel broken. Previously people could make a personal choice on chem vs ext and it would usually be pretty okay. Now I get scared when someone on my ship has an extinguisher, or when I have a low level on my ship. Right now everyone has to be involved in keeping the chem up, which doesn't feel good.
Essentially, previously a flamer was like any other individual weapon: dangerous if you ignored it long enough, but something that could be combated by decent engineers. Now it feels like ignoring a flamethrower for half a second leaves you with nothing: no balloon, engines, guns, or armor.
The fire stacks are a really cool concept, but the speed with which they grow feels absurd, even admitting that I was a fan of having a higher stack growth.
In my opinion there are 2 directions to go with this: nerf the flamethrower some more, or buff fire tools.
Nerfing the flamethrower reduces its ability to be used as a feature weapon, but makes it less abusive to anyone who doesn't intimately understand the game.
Buffing fire tools places more responsibility on engineers, making it a higher skill weapon to fight against.
I am more a fan of nerfing the flamethrower a bit in 2 ways:
Start cutting into the range a bit
Lower the fire stack chance (again)
Right now it isn't very fun. You are fighting fire, not the enemy. It may not be strictly OP at the moment, but it is too strong in a way that makes the game less fun (in my opinion)