I've been living the same life for a while James... my advice would be to let her drive the car for now, but you need to pull waaay back. Why were you shopping for presents together? That's an awfully emotionally charged shopping trip, just dripping with poignant moments and guilt triggers.
I understand the need to get it done. My W and I had about a 30 minute convo on what to get the kids while looking at their lists. She took specific items and I took specific items. We did not shop together. We created a shared spreadsheet in a Dropbox account where we could each update when something was purchased and how much we spent. We also agreed on what "to get each other", though really she bought something for herself (well, I picked it up since we got the kids the same thing and I was already at the store) and I bought something for myself. It avoided me picking out a gift for her which would've smothered her and really would've been very heartbreaking for me since I've always put a ton of thought into her gifts and it's one of my favorite things to do.
It's not about just not being in the same room, but about the looks, the comments, and "the feeling." You have to detach and get used to the idea of being divorced and not in an R/M. Once she feels that coming from you she'll feel better. My W finally said she feels better in the house because she feels I am accepting the D concept and making peace with it.
You can always move out, but that's fraught with all sorts of potential problems, both emotional and legal. If she is that uncomfortable she can leave. If she hasn't left then she must be able to deal with it despite what she is saying. I see her words as a tool to get you to do the leaving, since her actions are something else.
Married 6 together 8 Me:38 W:31 second marriage for both SS12, SD10, S6 Bomb: 9/8/11 (day before our 5 yr ann) W moved out: 2/18/12 D final: 11/12/12 Share S 50/50. Spend as much time as I can with SS & SD