I can see why you might say that, which is why I posted this in post 90.I'm not sure what you mean, or whether existence has to "come from" anything. I get the sense that talking about "the source of existence" might be a nonsensical statement like "the colour of the Cuban Missile Crisis" or "the width of time."
Maybe perhaps jumping the gun a bit there but existence being a source unto itself sounds like one source still and also to me sounds like a god concept, but of course we would disagree by that point.