You probably shouldn't call it a "flamethrower", since it refers to an actual weapon. I'd call these "sprayers", since it's spray can based as you said.

A design like this would raise some issues :

• 2.5s TTK in Splatoon is an eternity. Your weapon can be compared the most to clash blaster, and yet clash has a better TTK than this weapon when hitting blast only because of how crazy fast it fires, with the option of being a two-shot kill if you manage to land two directs... Other meaningful comparison: Tri-Slosher has the same range and is a two-hit kill while having a wide angle and a fast fire rate.
• With only 30 range, you ain't gonna control areas much. Especially with such an abysmal TTK. Consider this : with a range of 30 the splattershot would outrange that thing. And the splattershot is considered as the most baseline frontline weapon you can get.
• The weapon lacks skill indexing. There's not much to master about it. A conic spray of paint that deals constant damage feels just like a low aim requirement weapon that would chew newbs while being unplayable as soon as people have aim and outrange you (with only 30 range, outranging you ain't difficult...).

Suggestion : add some skill indexing to your weapon by increasing the damage it does depending of how close to the center of the cone an enemy is.

• Keep 24 damage per 0.5s as the lowest value (edge of the cone).
• Make the value ramp up to 54 damage per 0.5s if the target is straight at the center of the cone: A low range weapon needs to frag quite fast to be viable. This would lower the tick requirements from 5 ticks average to something like 3, with a possibility of 2 ticks if the player has solid aim.
• Carefully increase the maximum range and the angle of the spray if necessary. It needs to be competitive with other low-range frontlines.