Well.. I just installed Assasins creed to my external HDD... There were no files over 4 gigs, But the game won't load. It just goes to a black screen... I tried searching for an answer... But I only get results for "brotherhood".
I have done some research on this matter, and most of the chatter is the same, as far as I can see the game will not work under any circumstances, and according to the jailbreak compatibility list it will not function at all, and your tests seem to confirm that.
This system modification for the PS3 is still in its infancy, and although it doesn't work now, whats to say, once custom firmwares arrive and the ability for NTFS hard drives (so no 4GB limitations) that AC1 will work, we will just have to wait patiently for the experts to do their thing.