Is it permissible for me to give charity to my mother or to the poor from my husband's allowance, given that I am employed and my husband refuses to let me spend from my own salary?

There is no harm in your charity from your husband's money if he has given you ownership of it, allowing you to dispose of it as you wish. However, if he gave it to you for household expenses or similar needs, then do not give charity from it except with his permission, or according to what is customary. Your husband is not permitted to prevent you from disposing of your salary because it is your property, and it is better to seek his approval to gladden his heart, provided it does not cause you harm.