How to rename DynamoDB column/key
There is no real easy way to rename a column. You will have to create a new attribute for each of the entries and then delete all the values for the existing attribute.
There is no reason to drop your attribute/column, if you are having trouble querying the table use Expression Attribute Names.
From the Expression Attribute Names documentation:
On some occasions, you might need to write an expression containing an attribute name that conflicts with a DynamoDB reserved word... To work around this, you can define an expression attribute name. An expression attribute name is a placeholder that you use in the expression, as an alternative to the actual attribute name.