Hi,
This reply might not be of much help, but I'll give it a shot...
Unfortunately I don't know much about the savestate format or compression, but if you take a look at the source code it shouldn't be too hard to figure out. The reason I'm replying is because I wanted to say that FBAlpha has a sorta simple cheat search function under the Misc menu tab, that might be of some help. Also, for 68k games, there is a very basic 68k debugger under the misc tab, which can let you browse through memory.
best regards,
- dink