Oh hugs what a difficult situation. If I were in your shoes, having already had a baby these would be my options.....

1) Change Obs (by far what I would feel most comfortable with, as long as I felt comfy with the Ob, if that makes sense). I know it might seem tricky, but it is doable.
2) Go public. Keeping in mind that you need to do a whole lot of research into which hospital to choose, not *all* public hospitals will be low-intervention. Especially given that you have GD, they also might try to pull a shifty on you.
3) Hire a doula and stick with the Ob. Not really an option for me I guess, I wouldn't be trusting that your Ob will be willing to listen or negotiate anything much with you. Even with a doula, you could still find yourself fighting a very difficult uphill battle to get the birth you want.

However, a doula is a really good idea if you go with either of the first two options! I understand that it may not be financially possible if you change Obs, but if you go public it could be a really good option for you.

You guys sound like you've done a lot of research and are very well informed and sure of what you want for you and your baby. A tip - you never get a chance to birth this baby again. And a wonderful birth is just that - more wonderful than you could imagine. I still get a high thinking about my son's birth two and a half years ago (under the care of an Ob )! I know the money seems important now.......but you will likely feel differently after the birth. If you've come this far to be asking these questions......well, I can't help but think that you are better off without this particular Ob. Good luck