Wow...you really have a lot going on in your life.
With the relationship with your husband: There is really nothing you can do or say to change his actions and beliefs. He seems to be set in his ways. He displaces his anger about other life events onto you which is not fair but that is his nature.
With the relationship with your son: He is an adult now. You have raised him. It is now his turn to be the parent even if you do not agree with his parenting style. It is true that he did not have a good role model of a dad growing up, but that was in the past. Your grandson is still young and there is hope that your so may change his parenting styles.
With the relationship with your daughter in law: Let her be the parent. Unless your son and daughter in law gave you specific directions to discuss the academic and behavior issues of your grandson at school, then do not try and fill their shoes.
With the relationship with your grandson: Continue to be the most loving grandmother that you can be. It sounds like your grandson means the world to you. Continue to do all of the things that make him happy to brighten his world.
Overall, I think that there are serious issues in the lifestyle of your grandson with regards XXXXX XXXXX home environment. It sounds like he is not getting the love , attention, respect, and care that he needs to emotionally thrive while at home. Therefore he will act out at home and it will in turn carry over into his relationships at school. He behaves well with you because he receives all that he needs. He is still young, but things must turn around in his home environment.
It is hard to change other people. We can only change ourselves. I would suggest that you seek professional counseling to learn coping and intervention strategies on how to deal with all of these issues. It seems like the only person who values your existence is your grandson. But you have been the glue that has held the family together.
If you have health insurance, call the customer service department and they can steer you in the right direction for counseling. You need a neutral source to discuss all of these issues with. It is just overwhelming to continue to live the way you are living.
If this has helped, please ACCEPT. BONUSES are appreciated as well for my efforts. Have a great day!!!