SS, MY H recently asked the same probing questions about my whereabouts when I went for an innocent walk up in our neighborhood & ended up talking to some friends for 45 minutes.
I was vague at first but felt ridiculous not telling him. (I think he thinks I might be trying to talk w our divorced next-door neighbor!)
Anyway I agree that boundaries do need to be set. I think it is all in the TONE in which you set your boundaries they way they will be interpreted. Say it nicely, not defensively or rudely and it will more likely be received better. (Let me know how it goes b/c my H is totally cake-eating right now & I know it & haven't done the whole boundary-setting things either...but I've been thinking A LOT about it).
M- 18 T-21 S-14,11 & 10 BD 6-18-2012 (OW-EA) H moved out 11-3-2012 10-5-13 Me- I want a divorce. I want to move on w my life. 11-25-13 Jointly filed.