There are probably a lot of factors that we don't see, so we shouldn't be so quick to judge. Actually, she probably is not a troll, but someone who was venting and didn't select the best choice of words to do so. My humble opinion is that you and your husband need to have a very serious talk. Most likely he has "cold feet" if he was supportive at first and has only started to become negative about it very recently. For some men (especially if he is accustomed to being the breadwinner), it is a major blow to the ego to have to "follow" one's wife (some men are okay with it, but others are not). Moreover, his fears may be legitimate as far as fearing that he may not have lucrative job offers in the new town, especially if it's in a less densely populated area. But at the same time, it doesn't seem like forfeiting pharmacy school is necessarily the best solution either, as your future career as a pharmacist will be beneficial for your husband and especially your child, and you obviously weren't accepted into another pharmacy school closer to home or you wouldn't have this concern. Is there a possibility that you could contact the school that admitted you and ask about deferring your admission for a year while you sort these matters out? That gives your husband time to research job possibilities in the new area before relocating. It also gives you another year to reapply to pharmacy school (maybe you'll gain admission into the one closer to home).
Also, electing the help of your mother is not a bad idea. The support of friends and family is often an invaluable resource when one is completing a professional program...be it being there physically or just lending an ear. I don't know if sending your son away is a good idea, though. Not because he will be "in Darfur somewhere" as someone so ignorantly stated earlier (contrary to public opinion, there ARE places in Africa that are stable, modern, and affluent, and if she is considering sending her son there with her family, it is likley to one of those places, not to a war zone...don't make silly assumptions just because the word "Africa" was involved), but because he IS your responsibility, and because he is so young, sending him away will cause you to miss out on his formative years. If he moves over there and only visits with you on holidays, then he will come to view Grandma, not you, as his "real" mommy because of how seldom you will see him...and that would devastate most mothers.
I think if it's feasible to ask your mother to come here to help out, do so. It will be a great way for your child to bond with your mother, and it will also be a good way to ensure that he knows more about his African heritage in addition to his American heritage. I thank God that my mother constantly positively reinforces to my daughter the importance of being functionally bicultural, yet still having pride in being of African descent. But I don't understand why he said that she can't reside in your current house with your husband, your son, and the stepchild. Why should they all have to pack up and move with you...is he trying to "get rid" of all the kids so that he can have his "freedom"? I don't wish to make negative assumptions about your husband, but at best it seems like he wants you to handle all the "domestic" stuff (kids, etc) without him lending a hand. And that's not the purpose of marriage; marriage is a partnership and not a dictatorship. You two really need to talk openly and honestly about this very important issue.