BS(me) 46, Two wonderful teens.
My biggest worry with a trial sep like you are suggesting is that you are still totally tied financially. So, he goes out get his own place. Now, you have to pay all the bills for two places out of the same pot. If he does continue his behaviour, he's going to be grabbing money no matter what the bills are, and you are now not only going to end up emotionally a mess, your finances are going to get screwed too.
Doing up sep papers doesn't mean you HAVE to get divorced...but severing finances is a smart transaction business wise.
When my XH and I split, it was for good. But at first I just needed time to figure out what to do. So, I threw him out, which he was happy about because he could screw his tramp. He went and stayed at his brothers, who lives an hour north of us. His job is 40 min south of us. He moved up there, and continued to use my gas card to gas up the car. Cost a fortune! Never mind whatever money he was spending! So, I told him to come back, into the spare bedroom while we sorted out the finances. I immediately started splitting expenses up, so he would have to look after his own crap, and not be able to put me into a hole. In house sep was hell, but I worked on the money. End of July/beginning of August, I had enough of him ignoring the kids and I, sitting in his room skyping with the trash, so I told him he couldn't even bring that whore into my house on the computer. He moved out by mid August, by Sept 2 the sep agreement was done, and I had the house in my name only.
I would have loved, at one point, if he could have gotten his head out of unicorn fart land and become my husband again. But if I had waited, I would have lost the house and everything else. Remember, as long as you are still married and don't cut the finances, it's all marital debt. He can run stuff up, and although you may be able to get some of it back if you can prove he spent it in the whore, most of it will be considered Mdebt.
So unless with the trial, you control all the money, and he's staying somewhere that won't cost you a fortune, I say be very careful you don't compound the problem.
He is no longer my best friend. Repeat until it sticks.
WH says marriage is over: May 15, 2009.
EA#2 July 20, 2009. Legally sep: Aug 16, 2009. DIVORCED!!!! Signed Nov 23, final Dec 24, 2010, adultery listed.