Hi we're the developers of the Canada Post extension
Here is the link to the manual that will help you understand a bit better.
https://abantecartextensions.com/docs/canpostPlease note that we have not released a CanPost version to support AbanteCart v. 1.2.14 or 1.2.15 yet. Should be out in a short time - still in test as there were several cart changes.
Answers to your questions
1. Each product does not require a dim. But if your product is extra large, or large and lightweight, or you are shipping individually you should imput dims on the product page.
2. Unless you have an item set to ship individually, all items in the order will have the weight added to calculate the rate based on the destination
3. No - that requires a "bin" algorithm which which is beyond the scope of need for most AbanteCart users.
4. If you use a standard box size exclusively - you can set it in the Settings on the CanPost, you can also set max wt you want to set.
If those parameters are set within the Settings page, then if the total wt of your shipment is more that the set wt - it will use 2 or more boxes and calculate and total the shipping costs.
If you would like a test site on our server just sent a request to the email (link is under my name) or PM us on this forum. Let us know what version of AbanteCart you are using.
The Support Team
We Hear You 2, Inc (WHY2)