Will the husband be sinful if he wishes to divorce his wife due to her sharp tongue and disrespect towards him and his family, given that she is negligent in household matters, and she is pregnant and he has three children from her, and after numerous failed attempts at reconciliation?

The wife's insult of her husband and his family and her harming them are major sins. Likewise, her refusal to share her husband's bed is a grave sin that incurs the curse of the angels. We advise you to repeatedly counsel your wife with encouragement and deterrence, and remind her of the warning against disobeying her husband. If that does not work, then forsake her in bed. If she still does not desist, then strike her with a non-injurious blow if you believe it will be effective. If none of this works, then you are not to blame for divorcing her. However, if you are patient with her, there might be good in it, especially if divorcing her would scatter the children.