Does the patch give an error, or anything, when run?
FWIW, your save would load fine in the Developer's Cut version of the game. When D2:DC was first released there was an upgrade offer with D2:ED / FoV / DKS for a download version from the
Larian Vault. This was automatic on Steam (and eventually other digital distributors) and you could contact support about the retail version. See the topic
Divinity 2: Developer's Cut and Anthology on Steam.