fileMaker (native) supports only text mails, no formatted text/styles
to send styled/formatted text, one needs to attach a pdf (that was created by FileMaker) or a Plugin (among other methods like AppleScript, etc)
you can create a pdf from Your layout to the temporary folder, then attach that pdf to the mail. You'll need some knowledge with file-paths in FileMaker, but it's not rocket-science.
if Your people need the form inside the mail (no attachement), then a Plugin will be needed (MailIt by Dacons, MBS, others). Mailit comes with good examples, I'm not familiar with the other ones
if Your text is simple (no formattings), You can send the mails with that text - but from Your posting, it seems to be formatted text with different font types/sizes, checkboxes, tables, et all...
yes! there are feature requests for this (product ideas)
I personally love the pure-text-mails, I can read them all, everywhere - but today, people want to send mails that look 'modern'. Therefore, this feature is really missing in FM.
using methods like Plugins (especially the super - but somewhat complicated ones) are not for beginners - but beginners want create mailings too (and FileMaker tells everybody that there is no programming needed...)