Reinstall with existing /home LUKS

What I would do is to reinstall using /boot and / and leave the /home partition alone during the install. Once you have installed you can install cryptsetup, set up your partition in /etc/crypttab and /etc/fstab and you'll be away. I'll assume you have an encrypted swap For the details, once you have installed and rebooted, open a terminal and:

sudo apt-get install cryptsetup
cryptsetup luksOpen /dev/sda6 crypthome
cd /
mount -t ext4 /dev/mapper/crypthome /home

Edit the partition details and file system type as required. Now you can browse /home and ensure it is what you expect. Then you need to put the following in /etc/crypttab

crypthome /dev/sda6 none         luks
cryptswap /dev/sda7 /dev/urandom swap

And in /etc/fstab you need to add these lines to the end

/dev/mapper/crypthome  /home  ext4  defaults  0  2
/dev/mapper/cryptswap  none   swap  sw        0  0

Do a reboot to check it all works as expected and you're away :)