Hello,
1) Read the license policy https://themeforest.net/licenses/standard You can use the same license only if this is the same project (end product). If this is a new project you will need another license.
2) $39 is the best price at this moment that we could offer. The regular price is $59.
3), 4) You can try the Duplicator plugin https://wordpress.org/plugins/duplicator/
Regards