I wouldn't make too much of being "unsuccessful in locating her estranged husband". If they had been separated for several years by then, it was likely easier to post the required amount of times in the newspaper than it would be to try and serve him papers in person, with him likely being in another state. My guess is that posting in the newspaper that you are seeking a divorce is considered a good faith "attempt to locate," and after Avantae did that the required number of times, she would be considered "unsuccessful" for legal purposes, regardless of any other actual attempts to locate him.
To the public's knowledge, he was out of the picture before she began fostering/adopting the kids we know about. However, he was with her before
Robert Adams, whose teachings inspired the Infinity Institute, died in 1997, and a while after the
Infinity Institute was formed to carry on his legacy. It looks like Avantae's name is not officially associated with Infinity Institute until the IRS links in 2011, but I don't think it's a leap to suggest she may have been affiliated with the organization prior to that. If she was, her ex-husband may be able to shed light (to LE) on her affiliation with Robert Adams and if that has anything to do with this.
So far I think the only "official" connection--other than that it
feels weird--is that Robert Adams was a spiritual leader (though more associated with Hinduism), Infinity Institute is a spiritual group (though less specific about any ideology than I think Robert was), and the 911 caller said that Blake was religious, into meditation, and she believed he had gone to a Buddhism camp.