My apologies, I misunderstood the custom field group as an RFG.
Regarding the default value for the date field, you need to pass a valid timestamp instead of a string. For example, assuming the current_date shortcode is registered:
[cred_field field='data-evento' force_type='field' class='form-control' output='bootstrap' value='[current_date format='U']']
https://toolset.com/documentation/programmer-reference/forms/cred-shortcodes/#cred_field
Regarding the select field for taxonomy, that is available only for Hierarchical taxonomies. In that case, you will need to switch to the expert editing mode and add the following attributes to the taxonomy field shortcode ... display="select" single_select="true"]
[cred_field field='categoria-ticket' force_type='taxonomy' output='bootstrap' class='form-control' display="select" single_select="true"]
https://toolset.com/documentation/programmer-reference/forms/cred-shortcodes/#cred_field
The calendar image can be customized with the jQuery UI datepicker API. You will need to apply the image option for it, or hide the image.
hidden link
The Trash icon is provided by Toolset. You will need custom CSS. Let me know what you want to achieve and I'll do my best to help.
Regarding making the ID and date fields read-only. It can't be done without some custom Javascript code. And for the date field, I don't think jQuery UI Datepicker has a read-only mode.
This being said, I wonder why would you display these fields in the form if you want to set default values for them without letting the user change them. Why not using a custom code snippet, hooked to the cred_save_data action, and programmatically set these values?
https://toolset.com/documentation/programmer-reference/cred-api/#cred_save_data
I would like to hear from you about it. Why would you want to make these fields read-only, instead of completely hiding them or programmatically assign them?