I haven't installed freespire. For a multiboot situation, I would set up the disk partitions manually in the install program's partitioner. For openSUSE, in the disk partitioner program, you can opt to use all the free space for the last partition.
If you already have a swap partition, you don't need another one. The installer will even ask if it can use it during the install. If you have another Linux distribution, sharing the /home partition is easily doable. Just make sure you use a unique username, or append a modifier to your users home directory. For example, in Ubuntu you can have "/home/lolbob-ubuntu" and in SuSE "/home/lolbob-suse". The username and the users home directory are given in the /etc/passwd & /etc/shadow files. You could install suse with the user "lolbob-suse" and then after installing use moduser to change the username to "lolbob", leaving the home directory as "lolbob-suse". This way you don't have one installation trash personal settings of another distro. Also, the UID ranges for users may differ between two distros so a unique users home directory is needed but the /home partition can be shared.