I'm presuming that you've gone through /admin/webservice/documentation.php to list all of the available WS APIs on your server (as this will differ depending on plugins).
3) Two issues here: access conditions are created via a user control that converts the conditions into a JSON representation for storing in the database. I don't think there is a Web Service that can do this. In addition constructing the JSON representation for the rules that you want directly is *complicated*.
And that said there doesn't appear to be a web service to actually set (course_)module settings. This is probably due to there being so many different setting values that are module dependent
4) Providing you're wanting these as "manual" enrolments: core_role_assign_roles
You may want to consider writing a plugin that implements specific web service(s) that does exactly what you need it to do, as this will have access to the all of the actual APIs & database (if necessary), rather than the Web Service APIs. (https://docs.moodle.org/dev/Adding_a_web_service_to_a_plugin)