I already answered your question in your ticket. However, I am posting my answer also here. I hope it will help someone searching for similar issues.
The validation error that appears when the numeric value is empty comes from the WPF framework. You can reproduce the same behavior with a single TextBox data bind to a numeric value (like float or double). Basically, when the text gets changed, the framework is trying to parse the string to the corresponding data type, but an empty string is an invalid numeric value, so the error appears.
In order to avoid the validation error, you will need to ensure that a valid number is entered. Alternatively, you can hide the validation error template, by setting the Validation.ErrorTemplate attached property on the TextBox editor to null. To do this, you can create a custom data field that derives from DataFormDataField and override its GetControl method. There, you can get the TextBox and set the property. You can see this approach in the attached project.
About the decimal point issue, I wasn't able to reproduce it. Can you check the attached project and let me know if I am missing anything?
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