Since you are dealing with internationalization already, what form are you using for numeric data in the fields?:

9,999.99

9.999,99

Your C# code will need to parse with a specific locale, otherwise users changing their regional settings will result in differing formats.

This is a fundamental flaw in EAV models - interpretation of what is, effectively, free-form data that the database cannot help you enforce the rules on.

Even when it is only used for configuration, if the value is used as a threshold option like "Minimum Shipping Charge", it could come into calculations.

EAV is useful - it's great for options and configurations.

Not so good for the "designing a database within a database" idea.

But this problem of type-safety and validation has not yet been addressed to my satisfaction in any architecture I've seen.