1. You can create your own ad packs. Yes these relate to single ad placement. Only the membership packs relate to multiple ads.
2. There is no specific option for this in the ClassiPress admin dashboard, so it would require customization on your part, or a plugin if you have one that is compatible with the theme.
3. If you mean spam posts, this can be managed with moderation of ads based on your ClassiPress settings, but there is no word filter specifically. There is a built in recaptcha field for new registrations and you could use anti spam registration plugins to manage this as well if you wish.