The long and short of it is that Google has well documented instances of bribing/paying companies to not offer their apps on other stores, and Apple simply runs their walled-garden. Google deleted evidence of them doing this, which looks very shady. Also, the judge in the Apple case took an incredibly narrow view, something like "digital mobile gaming transactions". So Apple's 30% cut seemed to be in line with competitors.
Of course, I don't think either should be allowed to do this, but the legal argument against Google is stronger imo.
In medicine we are taught that the first line treatment for insomnia is treating the underlying illness—in your case, potentially depression— otherwise, CBT-i (cognitive behavioral therapy - insomnia).
So my first recommendation is to seek care from your physician for your depression.
Otherwise, there are well described self taught classes for CBT-i. I have told patients to check out the VA's website for this: https://mobile.va.gov/app/cbt-i-coach
It is a lot of the sleep hygeine described in another excellent post hew.