So we should only have settings like required_score in local.cf specific to what we want, and change the 10_misc.cf for the report part in /usr/share/spamassassin/
Does that sound right?
No.. you should leave 10_misc.cf in /usr/share/spamassassin and leave it ALONE. As I said before, do not edit anything in /usr/share/spamassassin.
10_misc.cf, and all the other files in /usr/share/spamassassin/, represent the program defaults. Don't mess with the defaults. Consider them part of the code.
You should use /etc/mail/spamassassin/local.cf, or some other .cf file of your creation in that directory, to change it.
First, do a clear_report_template to wipe the default report, then create a new one. You can use the relevant parts of 10_misc.cf as a shell to write your file from, but don't copy the whole thing, only include the parts of the file you're trying to change.
The general concept is that SA reads all the files in /usr/share/spamassassin/*.cf first, and establishes it's default as-built-by-the-developers configuration.
After that, it reads /etc/mail/spamassassin/*.cf, and here you can over-ride any defaults you wish.