If you want to increase or decrease rewards points with option change then this extension is best for you.

Its vqmod extension.
No file will replace

INSTALLATION:
Step-1 execute query
ALTER TABLE `oc_product_option_value` ADD `rewards` INT(11) NOT NULL DEFAULT '0' , ADD `rewards_prefix` VARCHAR(1) NOT NULL ;

Step-2 upload xml file in vqmod/xml/

If have any problem please let me know, support and installation is free at dyisolco@gmail.com