I would SUGGEST seeing a lawyer before signing ANYTHING. Probably no harm done at this point, but there may be issues of property or debt that you would benefit by having someone look over. You don't want to get stuck with bills he might have run up that you don't know about.
I would also suggest deleting any emails from him rather than having them sit there unopened. Do you have a way to block his emails?
Don't waste your time and energy feeling bad about the fact that he is filing. Some of the members here have had a terrible time extricating themselves legally from their marriages. One other thing--he might actually be posturing and then drag his feet in terms of getting anything finalized. I would push for it to go through. The sooner you wrap up this chapter the sooner you can go on to an awesome new life for yourself.
Hugs, hang in there. It's--and you're--gonna be OK.