The screenshots seems to be reduced in size, hard to read, but it looks like a parser error for the changed config file.it is complicated indeed, for first this appears when i try to load the game:and for second line 3 has a bad string
The RomPath line must look like this (including the quotes and the comma at the end):
"RomPath": "Sonic 3 & Knuckles.bin",
...assuming the ROM file name is "Sonic 3 & Knuckles.bin", of course.
Also make sure the ROM file is located in the same folder as the config file.