Sorry, but we cannot resolve the upgrade issue. It seems it is connected with the multistore, but is too entangled to be resolved within a reasonable time frame. The only option is to uninstall Pavilion 1 and install Pavilion 2 anew. You won’t loose any opencart data (products, categories, orders etc.), but you have to re-create your pages in the theme builder. Sorry for the inconvenience.
1) The multistore will work once it installed from scratch. The issue affects multistore upgrade from Pavilion 1 > 2 only.
2) You can copy your live site to a dev server as you suggest. You should uninstall Pavilion and then install BurnEngine and set up your site
3) After you have finished, you can copy BurnEngine package to yor live server, uninstall Pavilion module and then install BurnEngine. Then you should import the following two tables from the dev server to your live site – oc_burnengine_setting and oc_setting
4) Your live site should have BurnEngine installed without loosing orders.
P.S. Don’t use the BurnEngine version we uploaded to your dev server as it contains some debug code, which can slow down your site. Use the themeforest package.
P.S.2 Even if you try the above steps, make database backups to prevent unconsidered issues.