He ended up having to go to the vet (chaching$$$), and all is well now.
BUT just a quick update, I found out conclusively finally how he got ahold of string.
I kept the string (I know, gross) and noticed
a pillow in the house where part of the stitching had been scratched or chewed off, and sure enough it was the exact same diameter, wind, and length of what was missing.
So if you have any blankets or pillows and the like with stitching, and a rascal like Wesley, might wanna inspect them for safety.