try this or its hardware............ you do any deviation and you are on your own.
remove your external sdcard and dont put it back until you are sure your phone works
as per your above post you can access cwm
1: format data / cache / system
/ sdcard or emmc [system is a must]
2: format preboot / boot [cwm 5.5 or some alternat if option available]
3: download stock i9100 ROM from checkfus (prefer) or sammobile
4: flash using odin, after first boot dial *2767*3855#
5: do not sign in, use for half hour or so, if you think it works sign in to google.
6: do not restore any thing, no titanium backups/restores
7: do not put your sdcard
if your phone works now you know its not hardware now do whatever