Hi Flow,
Sometimes I feel like one … but it also helps that I have a list of reference posts that I use to answer many questions that have been asked before which also allows me to reply to many more questions than would otherwise be possible … but answering forum posts is still the time equivalent of much more than a full time job on most days. It’s also something that I enjoy which helps a lot as well 
You may have seen this already but post #2 here includes links to most of the better forum posts and topics about mattresses and children and includes links to many good options as well.
Post #21 here also includes a list of the better online options I’m aware of that ship across Canada that would also be worth considering.
There are also many good options or possibilities in the Montreal area that are listed in post #276 here.
Yes … different types of foam including polyfoam and memory foam can both be “punched” with holes to aid in ventilation. I have also encountered many stores or salespeople that have no idea about the differences between different types of foam and use memory foam and latex interchangeably. Of course memory foam has a much slower response than latex and is also temperature sensitive as well (to differing degrees) so telling the difference between slow and fast response materials isn’t that difficult and once you’ve seen or felt latex it’s difficult to mistake it for something else … even though there are many different types of latex.
Yes … Tempurpedic makes a wide range of memory foam mattresses of different types (which would all include different types and layers of memory foam in the upper layers and polyfoam in the deeper layers) but they don’t make any latex mattresses.
I would be very cautious with used mattresses or with mattresses that have been returned because of defects (whether they call them “scratch and dent”, overstock, or any other name) because you would have no warranty and you would have little recourse if you have any issues with the mattress. It’s not uncommon at all that you would be buying someone else’s problems. There is more about buying a used mattress in post #2 here and more about “liquidation outlets” in post #8 here. Regardless of where I was buying a mattress I would also make sure you know the type and quality of all the layers so that you know that there are no “weak links” or materials you aren’t comfortable with in the mattress and so you can make more meaningful comparisons with other mattresses. Sometimes “cheap” can be the most costly choice of all if you don’t know what you are really buying.
The pincores in a latex mold don’t go all the way through the latex so if a full latex core is cut in the middle then the holes may not go all the way through. There are also some continuous pour versions of latex that don’t have holes at all or where the holes are “punched” after it’s poured as an option. I don’t know what the blue material may be (a picture may help) but it could be some type of gel material.
Not off the top of my head no
I personally wouldn’t deal with FBM either. You can read about the reasons why in this post and this post and this topic (about their polyfoam and sources) and this post (presumably from a past employee).
Hopefully some of the comments in this reply will be helpful
Phoenix