I'm really enjoying this chain..
Liz - listen - you don't need grounds in your state to file. Thus, there's no compelling reason for you to say anything other than 'we don't love each other' or 'it's not working out as planned.' That's it. This way, your STBX will not feel the need to defend his choices and/or make inflammatory remarks about you. Once that happens, a divorce can easily become quite ugly.
I can't imagine why your STBX would be upset if you had friends over. Whether to mow the lawn, paint the ceiling or do the tango. Why do you presume that he would have an issue?
Similar to LdiJ, I'm not certain where there is a tax disadvantage to filing for divorce. File NOW. Believe me, you will not even be close to a final divorce by December!! Keep in mind that as long as you delay, your STBX will continue to accumulate debts for which you will be 50% responsible. Have you considered the liability you would be expected to assume if he were in an accident or anything remotely similar? Please file as soon as you can in order to protect yourself and your assets.