Of course black holes are theoretical. Just because we know that something created gravity waves that we can feel, doesn't mean that it was black holes as explained by theory. Even if it was something we could call black holes, it doesn't mean that we have the theory right. The whole thing about black holes is just talk, because we don't really know that anything that we know about them is accurate.
If for some unknown reason Mars simply vanished, we would feel the gravity waves from that as well. Detecting gravity waves is an itty bitty start. We still don't have any idea of what gravity or gravity waves really are.
God is just a theoretical concept, black holes are real...
Black holes are real from the standpoint that there is something there, whatever it might be. Black hole theory might be anywhere from completely incorrect to almost completely correct. The fact that black hole theory is theory, shows that the amount of correctness to our ideas of what black holes are is uncertain.
God is not a theoretical concept. Some aspects of God might be theoretical. Some attributes of God might be theoretical. God Himself/Itself is a scientifically proven fact.
There is more than enough evidence to know for certain that black holes exist... there is the dilation of light around them... the fast movement of stars that get near them... some of them even have huge jets of matter and energy spewing out both sides!
The only theoretical aspect of a black hole is what might be inside of it... sure, that's uncertain for the moment... but to say black holes are theoretical is a complete misunderstanding of astronomy (and scientific terminology in general)
Hell, even the Mayans knew about the black hole in the center of our galaxy! (the alignment of Dec 2012 was the alignment with the black hole)
To say it another way, some things that we call black holes exist. What they are, nobody really knows. Our explanation of what so-called black holes really are is theory. Being theory shows that we don't know for sure what black holes really are. If we knew for sure what black holes really were, we would have black hole law rather than black hole theory.
We are at square 1 with black holes, just like most cosmologically theoretical stuff. We know for a fact that something exists. We don't know much about whatever it is. The fact that it exists is law. The theory exists in our guestimations about what it is and how it works.
This is very similar for God. We know scientifically that God exists. Anybody who is interested might have theories about aspects of God. Religions that talk about God have something like theory about His attributes. They are, of course, a different kind of theory than science theory.
A wonderful point about all this is, like as there is scientific proof for the existence of both God and black holes, there is theory for both God and black holes. The factualness regarding the existence of both God and black holes, makes their existence law. The theories about both make both to be religion. So it is that modern science is a great portion religion.