I went with a dissolution, but that only worked because XPOS was willing to work together in a civil manner. If your WS won't be agreeable, a dissolution is not an option.
If you want him out of your life, you may have to bite the bullet knowing you may have to pay a price to accomplish that. Work with your attorney to strategize for the best possible outcome for you, given your state laws. That is what you pay them for. If you live in an "equitable distribution" state (that is what my state is), keep in mind that it does not mean 50/50, it means fairly distributed in the eyes of the court. That gives you flexibility, like NG said, to find a workable balance. Try to get the proof that he is giving the OW marital assets ($500/week) because that absolutely can be factored into the "equitable distribution" and could become a bargaining chip.
You can also think about marketable value of things like furniture, cars, electronics, etc. You can do a lot of "equitable" maneuvering with those values, i.e., if you are willing to give up some of those things, it gets offset in other areas such as your 401k. Also, check on your state's alimony laws. He may be making a big assumption there, depending on your state laws, because not every state awards it, or for extended periods. For example, in my state it is called "spousal support," and it is only allowed for a maximum of three years and only in cases where the spouse receiving it needs it to get themselves established (most times it requires the receiving spouse to be going to school full time in order to learn a marketable skill and if they stop going to school the SS stops). I had an employee that just went through that very scenario.
Ultimately, you just have to decide what you are willing to "pay" to get out of your bad marital situation.BS - Me
XPOS - too many OW/OCs over 20+yrs
Kids - DDs 23,18 -DS20 Deceased
M Dissolved 2013
This above all: to thine own self be true, and it must follow, as the night the day, thou canst not then be false to any man ~ Shakespeare, Hamlet