Grub can boot FreeBSD and that's the way I'd do it because I'm more familiar with Grub. I gave up on FreeBSD because of driver problems but I was able to dual boot it with Ubuntu and you should be able to do so as well. Here is a post found by googling.
Regarding partitions, you can make any setup you want because both Linux and BSD can boot from logical partitions. So you can have 1 extended partition with lots of logical ones, or 3 primary partitions and 1 extended partition. It's up to you. Update: in a comment AlexD stated that FreeBSD can only boot from a primary partition. I'm not entirely sure about this but he is probably right. In that case you should spend 3 primary partitions for BSDs and logical ones for Linux (I'm pretty sure Linux can boot from logical partitions).
fdisk deserves a separated question, but have you ever really tried to use it? I find
fdisk pretty straightforward. If you find it complicated you can try a live CD with GParted. The openSUSE live CD should have a GUI partitioning tool as well, but I'm not sure (I'm more familiar with Ubuntu).