OpenCart: Synchronize Products (and photos) between 3 OpenCart v2.0.3.1 websites

General information for the website: We sell electronics online
Description of every page/module: We have 3 websites which sell the same products to different markets (one is wholesale, one is retail, etc).

Presently we have to create the product three times and when we change a detail, eg the price, or the "Out of stock status" (eg to "Discontinued") we have to update it in three places. This is very time consuming!

(Open Cart Multi-Store functionality has been considered and ruled out for a number of reasons.)

We want to have a synchronization routine which we can run (or perhaps it can be triggered by a CRON job or similar) which synchronizes the three websites. We consider one website our "master" website, and the other two will be "slaves".

In some rare cases we might want a product to appear on one website, but not the others. In order to control that we want to use the "Stores" flag in Open Cart (https://snag.gy/3uU187.jpg) on our "master" website. (We enabled that flag on our test server by activating multi-site by adding a second store, but then not actually setting it up).

By default all stores will get the product so there will be 3 ticks. But if we want to stop it appearing on a particular web site (including the master one) we can just untick it here and run the synchronization and it will no longer appear on that website. It should exist on the others but be hidden using the "Enabled/ Disabled" flag.

Photos, prices, wholesale prices, etc should be copied.

References to the website's name should be automatically excluded however. For example if the product meta title on the master website says "DJI Phantom 2 Vision + - Buy now from ABC - The Market Leader" that text should be changed to say "DJI Phantom 2 Vision + - Buy now from XYZ - Your Wholesale Partner". Perhaps a regular expression can be used to search and replace the name/ slogan for each website.

The same is true for internal links. If the product description contains a link to www.masterwebsite.co.uk/dji-phantom-page it must be changed to www.slavewebsite1.co.uk/dji-phantom-page during the synchronization process.

We also want to be able to have different product descriptions on each website so we need two new product description fields and boxes on the front end, like this screenshot: https://snag.gy/sIjUfi.jpg (This could be done by our inhouse web engineer if you are not able to do this.
Description of requirements/features: The main features are this:
1) Master to two slaves: Synch all products including all fields (prices, wholesale prices, discount prices, manufacturer, photos, product description, meta title, meta description, etc, etc)
2) Change any mentions of website name/ slogan to match that website. EG "Buy now from ABC - The Market Leader" on the master website should appear as "Buy now from XYZ - Your Wholesale Partner" on the whole website. (This data could be stored in a database field or config file which we can update as necessary.
3) Change any internal URLs in the same way - eg change www.masterwebsite.co.uk/dji-phantom-page to www.slavewebsite1.co.uk/dji-phantom-page
4) Use Links > Stores flag in Open Cart to control which of the three websites products appear on.
5) Create two new database fields and two new text boxes in the Master website UI to control the product descriptions on the other websites.
Specific technologies required: Open Cart, PHP
Extra notes: