For comments, other than the info provided here (https://startupwp.com/topic/removing-comments-from-pages-and-posts/) there isn’t much more we can advise. Looks like you’ve resolved though.
1. The divider looks good, suspect you’ve now completely resolved?
2. Correct, what you just described for comments is native to WordPress core and the theme, not a plugin.
2a. Simply copy over comments.php to your child theme and make the changes.
2b. Same as 2a.
2c. Simply wrap the asterisk like so:
For live comment preview, you could try this plugin:
3-4. We’ll get back to you on these.