you could just download the program (since it happens to be free) and try it, but, um... here's the skinny on wax (which I use almost exclusively)
You can import .3ds models (though it's functionality for using them to make an actual movie is somewhat nill, as you can't make any changes at all to these objects).
You can use a 3d plane and stick your video track on it, then resize that plane, and you will be able to size, rotate, position change opacity.
You can blur, you can use greenscreening (or any other color screening that you want).
Not sure what multiplying is/means but I bet it can be done.
The biggest problem with wax is it's learning curve. But, just like with Anim8or, if you take the time to go through a couple of tutorials, you will be able to accomplish quite a bit.
There is another software out there called Jashaka. It looks promising, and has a few features that wax does not. It is open source and can be found at sourceforge.net
Jashaka's main issues are 1.) it's learning curve (it has tutorials and a help file though), and 2.) it looks like no one has done any work on it in a year or more. I am not sure if it's an abandoned project or not, but, if they are working on it some more, I can't wait for their next release.
Your best bet (for now) though is to use Wax, it's learning curve is a bit less than Jashaka's, and I find that, even though their message board is slow, you are more likely to get an answer to questions there than you will with Jashaka users.
Sage