The closest you can get is to package your iPhone web app as a native app using Phonegap.

I would shudder at the thought. You already have it built and have no use for the iphone development environment so there is no use to accept the hefty split in purchase price with Apple. Only positive is getting listed in the App Store. And the usefulness of that is getting more doubtful as the number of apps increases.

no. I suppose you could if you made an app that was nothing more than a wrapper around a web view, but I don't think that is what you mean.

I don't think so, but perhaps you can charge for a subscription fee or one-time payment through your site?