Thanks for reaching out. Let me answer your questions.
1. I do not see that issue on my end. If the field is newly created without any value saved before, then after you save the post, there is no empty value will be saved. Can you please share a screen record of this issue on your site?
2. If the setting save_field is set to false so we do not need to know what the field value is. The field will not look in the database to display the field value because it is redundant/unnecessary.
You can use the setting std to set the default value for a field in this case.