found it!
So for 3, a quick workaround not involving Theme customization is to Add new elements to the Webform.
I recomend use “Advanced HTML/Text” elements following the next example configuration:
https://mattermost.web.cern.ch/files/swhhsz594fr8mjbswnur7jsmsc/public?h=5-egV-QgthOk_VoZEahTBA16TkObEhGcKOQZOCiBa9c
Then a little change in order them to appear on the PDF attached to each submissions, change the View mode to HTML on the Attachment PDF element of your webform
Once done that the final PDF should include also images like:
Still many things to concretize but I hope this helps you on your implementation.
Cheers.