Also, for completeness/if anyone finds this via search:
After you place the patch files with your Genesis ROMs, you'll need to hit the X button in the game list to display all files -- the patches are not displayed by default.
As far as cheats for FCEUX -- all you need is the Game Genie ROM, which you have to name "gg.rom" and place in the /usr/local/home/.fceux folder. Then, in FCEUX under Settings, Main Setup, set "Game Genie" to 1, and the Game Genie will boot first.
Thanks again!