As you’re already using a child theme (Forefront), I wouldn’t suggest making any changes to it, as those changes will be removed if you choose to update Forefront at any time.
Are you really wanting the subtitle to go below the title and above the post meta? If not, it would be easiest and most efficient to just include it at the top of your content?
If you really need it above the post meta info, I should be able to come up with some sort of solution.
Let me know 🙂