For 1, I don't know of any good workarounds. I think it might be wise to have an intermediate page that says: "You are about to see a dialog box that looks like

For 1, I don't know of any good workarounds. I think it might be wise to have an intermediate page that says: "You are about to see a dialog box that looks like this, click on 'Trust' when you see it". That way fewer people will be scared off. Having a "tutorial" page is pretty common in other websites that have some kind of trust/installation process.