Overall, I think the evidence that Dabi and Toya are the same is too great. With the gaps in both their profiles (age and name of quirk). Dabi’s over-familiar tone with Shoto and Enji. His flame being stronger that Endeavors. The best evidence against this theory can be explained away...
2 He "Died" In The Past After BeingCompletely Incinerated By Flames. Dabi is a victim of abuse from his own father, Enji Todoroki, who only saw him as a tool to accomplish his goal, and that was to surpass All Might one day.