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Yes,you have to use it in FAT32 format.Read more here,maybe it helps:
http://talk.sonymobile.com/t5/Xperia-Tablet-Z/External-Storage/m-p/737961#U737961
I really cannot say a max size,I have read about people using 1 TB HDD,really do not know about SSD.You could look for Seagate,Toshiba etc.
Yes,true about that.You are sure of some quality after all.You should contact xperia care and gather more info about the size of the SSD supported:
http://www.sonymobile.com/global-en/support/contact-us/
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