There isn’t a way of filtering for the users that follow a Twitter user without using the Twitter API, however the rest of your query is do-able.
With the Demographics augmentation turned on, separate each filter with an OR logical operator. Consider using interaction.mentions (to get tweet and retweet mentions), twitter.in_reply_to_screen_name, and twitter.retweeted.user.screen_name. There may be other Twitter targets you find useful.
Your CSDL might look something like:
interaction.type in “twitter” AND interaction.mentions in "screen_name"
OR twitter.in_reply_to_screen_name in "screen_name"
OR twitter.retweeted.user.screen_name in “screen_name”