Sharren... Will you accept similiar complaint on your father by the wife of your brother? You will certainly will not accept such a complaint and will do your best to make your brother divorce his wife.
Please retrospect or talk to a counsellor and really assert that you are making right judgement about your FIL and not misunderstood him.
Because, some women are so much sensitive and afraid that they doubt almost every man under even slightly abnormal circumstances.
Do you know it is common among aged persons especially those who lost their spouse, will lose their mind and do such mistakes like not locking door properly or drop food while eating and many such?
So, Please. Please. Please. Take time to analyze and take correct steps to save your marriage.
Even if you finally find your FIL as bad, you can still take steps to fix this by not hurting anyone drastically.
But if you hurt anyone by mistaken judgement, then everybody's life will be ruined.
Please. Please. Please take time.
I wish you peace of mind to you and to your family.