Hi Jen,
I only have a few minutes so please excuse the “short and sweet”.
First, let me ****** you – you are not alone.  Yes we (F&Fs) know the awful emotions you speak of. I’m sure you have been reading some of the stories here. The cross addiction type behavior you speak of is apparently not uncommon. Just off the top of my head – Madge’s thread speaks to that…
Keep reading! You will learn how each of us has dealt with this addiction in our own ways, yet with the same running theme for the most part – which is to take care of ourselves.
CGs can change – but we can’t make them change. We can only change ourselves in order to step out of the wreckage the CG will have to deal with if they do change. In focusing on our own recovery, we remove the addiction from our lives and begin to live again. I promise, it can happen.
I will try to post more later – but seriously … keep reading here. You will begin to see what it means to “take care of yourself”. You are already seeing that you need to take care of yourself financially – and you absolutely do.
I am not an attorney, and I don’t live in Michigan, but here is a site for you to begin exploring the idea of filing for ‘Separate Maintenance’ in your state possibly on your own.
If you know of an appropriate attorney, or can have one recommended, most will give you a free consultation. You can explain your circumstances and concerns (and be completely honest) and what you would like to achieve. They can at least give you an idea of what your options are and the expense you can  expect should you decide to go down that road.
Keep educating yourself Jen – and try to focus on your own recovery.  You are stronger than you may believe right now and you will get through this.
 "… should I give up or should I just keep trying to run after you when there's nothing there?"  Adele on writing Chasing Pavements