If the unmodified files are fine, then it is your changes that lead to the problem. You need to make sure you only ever edit such files with a plain text editor most graphical editors are not. You have likely broken the force field files due to incorrect parsing.
You should not have to add any parameters to any force field files to account for PEG. The bonded interactions and atom types are core CGenFF and are already in the CHARMM36 port.