Great job in being non-committal, friendly, flirtatious, and cautious -- all at the same time. I know it's damned difficult.
I think your wife is at the "conflicted" stage. My advice would be to try a two-pronged approach:
1. Stay firm legally. Do not give up custody, but perhaps offer a "re-visit things after 90 days" thing.
2. Stay NICE -- in fact, err on the side of being WAY nice.
I'm suggesting this for a reason. It should quickly help you ascertain whether your wife's newfound niceness is sincere, or if it's just more manipulation designed to get you to soften your legal stance.
Puppy
P.S.
3. Do NOT, under any circumstances, have sex with her! If you do the above two things, she will either:
a. Work with you nicely, in a spirit of compromise, further showing her changes are sincere;
b. React negatively and immediately, showing you she WASN'T sincere; or
c. Try a different tack, when she sees that this one isn't working. That tack is highly likely to be her trying to seduce you.
