Yeah, a lot of these cards need some heavy tinkering/balancing. For example, the second creature can easily be balanced by changing its ability to prevent limitless growth (e.g. "Gains +5/+0 if you own at least two other Fire creatures"), the "absorb" mechanic seems more Life/Water/Darkness to me than Fire (though that can be fixed by renaming it to "consume" or "raze"), Pulsating Lava seems extremely OP, and Wall of Fire has problem in its card text (too much math, doesn't sound like a shield) so it can be simplified (e.g. to "Shield: Attacking creatures also damage their owner equal to 25% their ATK." with rounding up implied but not on the card).
All in all, I suggest just focusing on 1 card idea at a time and making a thread of the card you're focusing on in the Smithy. This way, you'll get the most feedback for each card.