Plz help stuck on DFu mode black screen

Hey guys, i need help i have i-phone 3gs fw 3.4.5 bb 5.16.02 , i decided to jailbreak and unlock it , so i downgraded it to 4.3.3 , jailbrake and changed bb to 6.15.0 , since i did that the iphone didn't boot and stuck on black screen , i put it on dfu to boot tethered but every time i try redsn0w stops and tells waiting for device to reboot , tred to restore but keeps giving me errors ( 1600 , 1601 ) , i have tried every thing , reinstalled itunes , but still stuck on this black screen and won't boot at all, so plz i need ur help soonest.
thanks in advance