I know, I have no expertise on the economic arguments, either. But I think it is fairly strongly evident that EU Regulations do have an effect on small businesses, constrains them, increases costs, etc, to an extent that can otherwise be absorbed by larger businesses. I don't see how that can be dismissed, even apart from the fact that they are regulations created by an unelected, supranational entity, and so come out of nowhere for them.
The industry thing is hard, and I'm largely thinking of the rules that have prevented a grand bail-out of the Port Talbot steel industry: EU anti-competition rules partly put the nix on that. Port Talbot now has a surfeit of skilled workers, not a lack of them.
We've opted out of ever-closer union, but it seems beside the point, and the main EU players treat that with contempt. I think it must be acknowledged that the whole point of the EU is integrated political federalism, and the most passionate Europhiles on all sides desire it to greater or lesser extents. This is why the pro-EU side has seemed to lack the polemical passion of Leave: they know it would be political suicide to push the Euro-federalism argument hard, because it is deeply unpopular. Now I'm conflicted on this: the federalist argument attracts me because I despise Nation State nationalism and I strongly relate to a pan-European identity, but it also worries me because in its current trajectory it is a fundamentally un-democtratic project.