First let me say what a spectacular job you are doing! You are changing your life for the better and in doing so, probably doing the same for your children. Congratulations on your success!
The divorce rate for bariatric patients is high. You are making changes that can affect your entire family's life style; your husband is fighting these changes. For your sake and the sake of your children you need to decide if you are going to allow him to sabotage these changes and potentially your continued success. His other choice is to hop on board and be a part of something wonderful.
I don't know a lot about bipolar disorder but it sounds like a really convenient excuse to blame his sh***y behavior and allow a vicious circle of verbal abuse to continue. If it truly is his bipolar he needs to figure out a way to fix it, be it meds, counseling or both.
Please don't allow yourself to get sucked in and try to deal with his insecurities. You will never be able to fix it, he has to want to do that! You can support him but you can't do it for him.
Good luck!