I went through this and hadn't seen him in months. He was living with the OW by then. I was scared to death!
The main thing is to keep in mind why you are there. Finances. You are fighting for your future, for money that you are entitled to.
Go prepared, by having figures written down, if you each didn't have to do a financial statement. If you are getting support, go for a number higher than you need because inflation will soon eat it up.
I sat across from my now ex and we each had our lawyers. He was dressed in clothes the OW has obviously picked out.
His lawyer started going over his expenses and it was all lies. I saw red. I am usually a very shy person but this yanked my chain, so I said that I knew he was splitting all these expenses with the OW because he told me so himself! His L put the paper away quietly. My ex made a low offer and my L said, "If you don't help her, she will be living on dog food." My loving husband of 30 years just replied with a shrug. BIG MISTAKE!
All my fears went out the window and I was fighting for myself. He made a bigger offer. My L and I went to another room to discuss it.
She said, "Did you see how he is sweating? His shirt is soaked under his arms to his waist." I counter offered for $100 more/month and he accepted.
What I am saying is, this is not the time to think about/discuss your pain etc. Believe me, those issues will sort themselves out, but you still have to pay rent and feed your DS. Keep that goal in mind.
You can do this! If I did anyone can.