I've seen a tutorial for "make your own self hosted firebase with feathersjs", have you considered just finding a self hosted alternative to parse and altering your application or writing a wrapper?
It is my understanding that Parse itself is now open source, so I could self-host the genuine article. The reason I don't is that I really am done with that project. In fact, I'm done with Android apps altogether. I currently am working on a much better project (website).