I think the theory with Dabi is that he was from a previous marriage with another fire quirk user. It failed and that's why he set about building up Todoroki as someone with both fire and ice. Another suspicious encounter was when Gran Torino assaulted the league and revealed all their real names... except Dabi who was already knocked out. There's definitely something up with him. Again, it's plausible, but there's not enough information yet.
And as for the anime, I seem to be in the minority, but I like the second OP way more than the first. I dunno, I just didn't care for the song much. The visuals were well done but the music didn't feel like a good fit. I think this OP and the two EDs hit the MHA vibe a lot closer to what I imagined.