External SSD as bootdisk

Hi,

I'm going to boot my iMac from an external SSD in a Thunderbolt enclosure. The internal disk is a 2 TB 7200 rpm. 10.9 is installed on the internal HDD. I want a clean install, there's no important files on either the internal or external as of right now.

Q1: I guess the first step will be to format the SSD in Disk Utility. Which format?

Q2: Do I need to partition the SSD? It's a 500 GB EVO 840. I do not plan to run Windows.

Q3: I guess I'll have to download the installer to the HDD, and then install to the SSD. Am I right? Something I need to know about this part?

Q4: I will use the HDD as a disk for media files etc. Should I leave the disk as it is today, or reformat it? If so, which format?

Q5: Is it wise to clone the SSD to the HDD once a week or so, in case the SSD fails and I need to boot from the HDD? Or can I boot from the HDD anyway? If cloning is a good idea, should I partition the HDD?

Thanks a lot in advance!