Using CSS Form Builder you will have a couple of choices for making the edits you would like. For the validations you can always run the validation wizards for both client and server side.
To edit the form and add in these other parts though you would need to first highlight the form then go to Insert > WebAssist > CSS Form Builder > Insert form.
The group that you would like to add to the form is the security group, the date picker can be added as a single form element.
When you use the CSS Form Builder it will recreate your form based on the settings you have chosen. You have flexibility over the design and the other aspects but the form will be created based on these. One thing you will have to do after you modify the form is to make sure to re-associate any default values for the form elements through the bindings panel.