The EU budget is rather a lot bigger than the UK's contribution. Your entire argument seems based on ignoring this, and seems determined to make it look like the UK's money is the only thing keeping the EU together -- and that, without it, they would fall. Perhaps that is a slight exaggeration, but only a slight one.
There is a wide world out there, indeed. But the EU is close to us. Far too close to ignore. It's not a Remain principle to claim that, it's merely a statement of how economics and global trade works. Called the "gravity model" -- look it up, one time, since it predates Brexit by some distance, describes global trade patterns wonderfully well, and isn't a remain plot to scaremonger you.
This is not even to mention, of course, the 40-odd trade deals that the EU already has with the rest of the world -- and that we have access to already; all of those we lose on the instant that we leave the EU without a deal. Most of the Trade Secretary's job, so far, has been trying to ensure that these trade deals are replicated on our departure. He has not had that much luck. The rest of the world tends to prefer dealing with the EU as a whole, than Britain separately.
Perhaps that's yet another group of people you should give more consideration to.