i think there's no ps3 that has a model number of 7d, you could find it underneath the console if you have the slim version (not the superslim version). It should be like "CECH-2XXX" So if you have the ps3 slim with the digit of 2 on the start of the numbers, well you have a chance of downgrading it then do the jailbreak. ps3s with like "CECH-3xxx" are unjailbreakable and undowngradable.
But you know what if you really dont have a chance to have custom firmware, well sony's official firmwares are for yours. you could buy second handed games or trade for getting cheap games. and of course, worry-free of getting connected to psn online.
Another question, does your console is still usable? what do you mean to the error message "data is corrupted"? can't you get to the xmb?