In answer to your questions:
1. By default, ad packages only allow for configuration of price and duration, but they are for unlimited ads.
2. There are no options within the theme which can manage this other than simply adding a custom field where they can input their PayPal information. Outside of this, there are
ClassiPress child themes available in the AppThemes marketplace which offer woocommerce compatibility you may wish to look into.
3. Added through customization, but this is not a current feature.
4. You can create custom fields in the ad listing form using the
custom fields and forums functionality.
ClassiPress is not encrytped, so you are essentially free to make modifications as you wish. AppThemes does not offer customization services, however we do have a
certified partners page where you can find developers for hire. If you make contact directly with an outline of your requirements, they can provide a quote for the work. Thanks.