Catz, I also think that growth will have little to do with you still working, especially like you say if your job is not manual. If she is that concerned about baby's growth, she should refer you to the hospital for a scan, which is a much more accurate way to measure baby's size, which is what happened to a friend of mine, and she had a 7lb 12 baby which is not exactly small!
I have known people to work right up to due date and no problems with baby. She should not make you feel guilty about still being at work, particularly if you want to maximise the amount of time you have off work with LO after delivery, and also since most first babies are late too! If you still feel fine, then work is not an issue.
Also, I don't understand why a bleed at 27 weeks would rule out a water birth, so please list it in your plan as something you would like, and the hospital will review your notes and let you know if its not an option when the time comes.
I can see your DHs point about the plan needing to be flexible, as in the end, the most important thing is for the baby to come out healthy, but the plan is more a "wish list" and also to do with pain relief options. I had a birth plan last time, and it helps the midwifes understand your feelings and wishes, so they know how you will react if things need to be done differently e.g. episiotomy. It is also good for putting down things like whether you want to check the baby's sex for yourself or whether you want them to tell you, whether your DH wants to cut the cord etc, so hopefully you can get some input from him, if you want to try again. But in the end, if he doesn't want to help you, then you should consider what you want.
Hope you feel more positive and empowered soon. Hugs.
PS Can you tell I am having difficulty sleeping- its 3 in the morning!