How do I use the developer tab to create a form fill email?

I've worked in Word and created form fill documents. I may send 25-50 documents a day as reminders to my customers that I need their help with similar but slightly different issues. Customer A may need to move their product to a new location. Customer B may need to clean up their product, etc... Because of the volume of letters I send, I've made a master form, with form-fill check boxes beside the specific issue I need them to work on. It's easy to factory/production line through 10 notices when all I have to do is open a pre-existing document, tab to the form fill boxes and complete just a few short items. This has steamlined my work tremendously. We are working towards changing our contact process and starting to send emails to our customers about the same issues. I know how to create an email template where all I have to do is plug in the email address for the specific customer, but I'm stuck at having 10 different email templates, addressing different issues, when I'd rather have one email, where I can check a box beside the issue that is specific to that recipient. I've gotten as far as getting the developer tab open, but I can't seem to figure out how to create a document and insert the check box, drop down menu, date selector, etc. Any help with that? Is what I want even possible?

Thanks!