1. it can be permission of the folder, try to change permission into 777 into this folder (/home/users/0/mods.jp-akirayun/web/hwansh/wp-content/plugins/jplugin//lib/twitter/cache/twitter.txt)
2. i don’t understand this question. you unable to see text editor inside visual composer? if that so, you can choose textblock element on visual composer. but if you don’t like to work with visual composer, you can simply click classic mode to bring back texteditor.
3. we unable to promise you anything about this request. because honestly we don’t see that twitter feed help people to explore the site. with latest feed will help people to explore the content easier.