Need to check the form, see if you can convert some tables to subforms with fields like table structure, if that reduce size.

10 mb is huge size for xdp, even over 10mb LCA file create issue while deployment.Is it only the number of tables contributing to size or you are also using images in xdp. 

I think there is no such property, to achieve this you need to write the script in the click event of the link/button.

Make sure you have made a flowable layout for the form and wrapped the fields inside the subform with a flowable layout. Some best practices for html5 forms:https://experienceleague.adobe.com/docs/experience-manager-65/forms/html5-forms/best-practices-for-html5-forms.html?lang=en 

I think you need to write custom validations for that.https://medium.com/@theopendle/aem-custom-metadata-forms-for-assets-8c6597205f9d 

See if this helps you,https://forms.life/2021/01/01/creating-multilingual-adaptive-forms/ 

In one of our projects, we created an email endpoint and configured a process to listen to this endpoint. Once you receive the email content/attachment in the process, you can play with this.

Hello Guys,I am Vijay Katoch and working with Bureau Veritas as a Module Lead. I have around 13 years of Experience in AEM.Mostly I work with AEM Forms and I love to work with AEM workflow and integration of AEM forms with different data sources. Also the theme feature in AEM forms is my favourite, ...

https://experienceleague.adobe.com/docs/experience-manager-learn/foundation/security/understand-cross-origin-resource-sharing.html?lang=en see if this helps you..

I think in the init event, the script should always take the current date from the system.