Well, you've got your work cut out for you.
I think the first thing you should do is bone up on HTML forms so you understand how to handle text inputs and checkboxes.
Here's a headstart on text inputs in a Custom HTML Prompt:
BOX - Tested.kmmacros (5.6 KB)
You can see a lot of your code isn't necessary.
As for handling checkboxes, take a look at Textcavator 2021 and see if you can figure it out. That uses quite a few form inputs, too.
If you get stuck, come back with a complete form that displays exactly what you want. Don't sweat the formatting (I used a table for alignment here) but do make sure it's got every field you want.
One thing to think about it whether you need to repeat the name/email field or just use the form a second time.
Anyway, good luck!