Penelopepea, I'll give a slightly different take. Our kid is 16, and we're in the process of divorcing, but we do spend most Saturday evenings together as a family, having dinner, watching a movie, etc. We have filed for divorce, so there's no ambiguity about getting back together, so your WS needs to reach that stage of acceptance, but it's possible to get there while still having some family time.
For a while, I had to be a broken record and emphasize to stbx that I wasn't interested in reconciliation. I also had to be the one to push forward on everything divorce related. It took him a few months, but he eventually got the message. In your case, just 2 months from DDay, it's preposterous for him to ask you to put it behind you. Most of us take years to process this stuff.
I think you need to be less diplomatic in your messages to him (I have a tendency, like you, to be "nice" all the time, even when I'm annoyed). Tell him flat out that you aren't interested in being friends or having friendly text chats. Not "I have to go," but "I don't want to have conversations like this." It can be hard to find the middle ground between amicable co-parenting and being a jerk, but sometimes you gotta bit harsh for them to get the message.
As for the "digs", way too soon to consider not dishing those out. 2 months is still in the raw, worst stages of recovery from infidelity. I think you're being too hard on yourself. Sounds to me like you're just reminding him of the truth by saying "you cheated!!!" He did! And there's no reason for you to avoid saying so.
[This message edited by NoThanksForTheMemories at 2:44 AM, Wednesday, December 17th]