What is Sabo's Power?
Based on Manga Chapter 744: 



Sabo is shown to have eaten the Mera Mera No Mi, and now has the Mera Mera logia-class power that can control fire. 

Thus until chapter 744, Sabo did not have devil fruit powers.

Since he is a part of the Revolutionary Army that is lead by Monkey D. Dragon, who also happens to have saved Sabo from the evils of Goa Kingdom, so Sabo could have named his attacks based on his training under Monkey D. Dragon.

As @Sp0t pointed out, Sabo has a strong haki that can be determined by the color of his body just before the attack that destroyed the arena ring in the Dressrosa arc.