Is it considered a sin for a wife to ask her husband to reduce his excessive communication with his family, and is this request considered a deviation from the sound relationship between a son and his mother?

It is your duty to assist your husband in honoring his mother and being dutiful to her, especially since she is attached to him and cares deeply for him. Your opposition has caused discord that led to estrangement and قطع. Therefore, fear Allah and beware of blameworthy jealousy. Be a support for your husband in maintaining ties of kinship. And your husband must not abandon your family or prevent you from maintaining ties with his family, for a wrong should not be reciprocated with another wrong.