is not telling her what i am going to do really the best thing?
Don't tell her, just DO it. Show her that you are not going to be negative all the time.
I def say to look into IC because it's going to help you sort out your own issues. Remember, you're not doing this for her, you're doing it to clear your mind and work on you. Working on your marriage apart from taht is also what you're focusing on here. What you do is tell her you want to make the M work, or willing to do any and everything to do that and if she doesnt' want to do MC, you respect that but you're going to do it on your own. Then pull back.
I would not advise you to move out, esp. if she's the one who wants the separation.
Feel free to read my sitch. My H is also very negative and kind of a "danny downer" or "negative nelly." As the other person in the M, I can tell you it is NOT attractive to us. So start finding positive things you like about yourself and stuff you like to do.