Seems to me you are getting two types of advice. One thought, expressed by "Love Bunny" basically says that if you want to have an open relationship you basically just have to give your husband an simple choice either you get what you want or he can leave. If you choose his course make sure you arer prepared for the worst possible scenerio. In her case, they apparently separated over it but got back together. There are no guarantees that will be your outcome. This option seems much more risky but only you can decide that.
The other option, I think expressed by Gala Girl is to keep talking in a non demanding way and see if things change over time. That way seems to give you more of a chance to maintaining your relationship with your husband at this time.
Non-monogomy cannot succeed in the long term if one of the parties feels that were threatened or coerced into it. My wife wanted to have sex with other men, and I was open to swinnging with certain boundaries that we both agreed on. I was fine with her doing anything she wanted, including sex with multiple partners, as long as the boundaries, i.e. no emotional committments, were kept. This worked for a while and then she wanted to change the rules to stop swinging and move towards I guess what you could call polyamory and wanted to start dating without me around or even knowing what was going on, claiming that was more fulfilling and exciting for her. Eventually, I had enough of that, I had never agreed to that and told her if we did not go back to our previous agreements that our long term marraige was over. My point is with no compromise and honoring agreements it is not going to work.
As others have said,it is what it is, you have two choices, go slow, talk, compromise, or tell your husband what you think you need and that that is the way it is going to be. Only you can choose.