You really need to take care here - you're skating on very thin ice! She's the first woman in his life, he trusts her and he's known her all his life, whereas he might only have known you for a few weeks. You have to handle her carefully - there's no point in going in all guns blazing the first time she's horrible to you. The more you criticize her, the more uncomfortable and torn he'll feel and the more likely he'll turn against you. You need to be strategic!
How to handle the monster-in-law
If you've done everything you can to be nice, get along and build bridges, but she still persists in hating your guts, then short of getting down on your knees and begging her to like you, there's very little you can do - so forget about her! Explain to him that the way she treats you is really hurting you and that if she's going to be like that then you want to see as little of her as possible. Don't go into detail: just leave it at that. Never stop him or your kids from seeing her, but if she's a real monster, you only have to see her at family gatherings or briefly, act civil and let off steam afterwards (with your friends, not in front of him!). If she really is a nightmare he should understand this, he won't make you put up with her and it won't cause problems for your relationship.
How to handle the mother hen
Give her a bit of slack as far as you can: let her look after the kids, look after him when he's ill (you hate him when he's got man-flu anyway!), feed the cats, water the plants when you're away, etc etc. Let her feel useful, but don't let her go too far: get a special ring-tone so you know when she's calling, don't reply, explain to her that you've made plans to go on holiday or do things together if she tries to interfere, and tell him you don't want to spend the whole weekend doing things with his mother...you'd much rather a long lie-in and 'quality time' with him (hint, hint). He'll soon get the message...
How to handle the NBF
The NBF can be really difficult to handle, because the last thing you want to do is hurt her feelings or appear unfriendly. But even if you don't fix your boundaries right from the start, it's never too late! Start seeing her less often and explain politely that you haven't seen your friends in ages and they're hassling you! Also, let her know that you're the one who knows him best now, so that she feels less 'in control' : "No, I think he'd prefer me in that one," or "We discussed it, but we'd much rather go away for a weekend." If you think this could work, try turning things around and diverting her attention away from your relationship by talking about her and her husband - give her a taste of her own medicine!