Thanks to your husband for his service and your family for their sacrifice & support.
Why would you allow someone who is mentally abusing your child anywhere near? Personally, if it was my child she would not have any access whatsoever. If she is going to have any contact with your chidren at all it should be at your discretion and only when you are present so she is not preaching at the children and telling them dreadful things about you & your husband and your immenent deaths at the big A or when your husband is stationed in harms way. As if the child doesn't have enough to worry about! It may be time to educate the child about the jw's, the pedophile issue, flip flops, deaths, suicides, immoratlity, unbiblical teachings, scandals, etc.... all can be done in an age appropriate way. Or just tell him grandma belongs to a dangerous and deadly cult and is crazy and you need to protect him from her, when all else fails tell the truth.