Ok, making our own trade deals - Liam Fox has already said that we will have exactly the same arrangement with the other WTO nations as we do now, so that ideal is sadly bunkem (we will also in all likelihood lose the fantastic trade deal we have both with the EU and the other nations for whom the EU has trade deals).
On immigration, we already let in more non-EU migrants than EU ones, and they are less beneficial to our economy. I can't fathom at all how we expect a government to do a good job of managing immigration when they already do a worse job than doing nothing at all. We have evidence before our very eyes but people choose to ignore it.
On laws, as has been said many times before, the world is a global place that requires global cooperation, so many of our laws are already determined by international bodies. This is certainly the case for those that the EU has any say in. As it is, all EU laws will be passed onto the UK statute book, so nothing will change (again).
On economic predictions, this seems to be a common feature on this thread, that if an 'expert' is wrong now and then, that means we discount everything they ever say. They don't have to be perfect, all they have to be is better than the alternative (which appears to be whistling in the wind). Doctors currently have a success rate of ~ 50% in terms of their decision making being the best possible option (due in no small part because of the pace of change and the number of new papers published), but no one would advocate going to your local butcher because doctors mess up. It's madness, and it's the same here. We're discounting pretty much every economist on the planet saying Brexit will be a crapshoot, on the basis that they didn't predict the credit crunch. Complex systems are almost impossible to predict with accuracy, but that doesn't mean we shouldn't do the best we can.