How can a mother keep a child away from a US Marine who recently returned home from deployment?

Our son recently returned home from deployment overseas and his soon to be ex wife will not allow him to see his 9 month old daughter. When he left he had been married 6 months and his daughter was 2 months old. He thought he was happily married and couldn't wait to return to his wife and daughter. 5 months into his deployment he called his wife at home to be told by their roommate that she was having an affair and he also informed him she was not caring for their child properly. Had proof she was staying with the boyfriend 4-5 nights per week who has a felony for ault and 3 misdemeanors for selling of drugs and under the influence of drugs and alcohol. He was also sent pictures of her with their daughter showing the boyfriend and his wife drinking at a bar with the baby.As soon as it came out she moved out of their house they were sharing with her best friend and her fiance. My son had to continue to pay the rent since there was a lease on the home for a year. He also continues to pay on their car she drives and her insurance and the car is only in his name plus he pays on another car. Then the Marine Corps made him pay her $1100.00 a month after she lied and said she was homeless. She was never kicked out of the house he pays for she chose to leave with her mother who also does not have a home. Even after she received the money she did not try to find a secure place for the baby to live. We have her bank statement showing she blew the $1100.00 in 1 week on eating out and buying clothes at adult clothing stores. Only $97.00 on the baby. Every month since when he is made by the Marines to pay the money she blows it on crap. In the meantime he just recently returned from deployment and he is broke because he is paying on everything and she is having a hell of a time. Still with no secure home for the baby just living in different places and in cheap trucker motels.The worst part is though is she is denying him to see his daughter. He has done nothing wrong except leave to serve his country and this is what he comes back to. We as grandparents tried to get temporary guardianship until he is out of the Marines but it was denied even though we had a ton of evidence of neglect. They pretty much said the baby isn't abused physically so the mom can keep her. Our court system does not look out for the best interest of the child as they claim. I just can't believe our system where are our son's rights. Nobody seems to want to stand up for this young man who has done nothing wrong. The mom acts as if he left to go party. She tells him he is not bonded with the child and he can't see her. He left for service to our country and how is he supposed to bond with his child if she keeps her from him. He is devastated. We have an attorney and he is going for custody but the date isn't until next month. In the meantime everyone is telling him be patient. How is this right. That is his daughter too and he loves her with all his heart and just because his wife decided to be unfaithful he is being punished. Nice way to treat our serviceman who fight for our freedom. We think this was a plan she had from the beginning and we here this happens quite a bit to our military men. Any suggestions on what can be done would be appreciated because right now it looks like the good guy is getting the shaft and the bad guy is having a hay day. This is just not right! His wife does not feed or anything so there is no reason he can not have her, in fact she admitted in guardianship court that the 9 month old eats her table scraps off her plate she does not even eat baby food. What kind of a mother does this. You can see why our son and us as grandparents are so concerned. Please give suggestions. We need to protect our granddaughter and our son and we just do not know the proper way to go about doing this. We have the attorney but it just seems as if it is taking a lot of time and he has spent enough time without his daughter it is now time for him to see her.