Use custom text first on homepage rather than excerpt

My homepage (www.thegamehaven.com) has some text on it which gets mined for use in the og:description field, but I’d rather not use that. I have some text in the footer I’d like to use instead, and I put that in the custom text field as well. what would be the best way to set it to use the custom text instead? As i understand it, the priority goes:

From post/page excerpt if it exist,
or from post/page content.
From category/tag description on it’s pages, if it exist.
From tagline, or custom text, on all the others.

could i perhaps set an exception to have custom text used first on the main page? and how would I do that?

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