As far as I know, the installer isn't able to split your installation up into multiple partitions like that. Your best bet is going to be to install AVLinux to the ssd (a fresh installation uses about 8 Gb), then set up your partitions and copy home and var into their new partitions. Then, set up your /etc/fstab to mount your new home and var partitions to their proper places. Finally, rename or delete the old home and var partitions (you may need to do that from the live DVD, it's been a while since I've done this), and reboot.
Here's a guide for more information:https://help.ubuntu.com/community/Partitioning/Home/Moving
That's for Ubuntu but it should work in AVLinux as well.