East, I can sympathize with your NGS tendencies and being afraid of the XW.
What can she do to you at this point? Take you back to court, get full custody, sue you? Think about why you're afraid. Run each scenario through your mind. And the hardest part ... try to come to terms with each scenario and accept it.
The calling thing is obviously not working, and it puts too much pressure on D7 (and you). Do you get to talk to D7 twice a day when she's with XW? If so, how talkative is she with you?
I feel like I'm sensing a lot of jealousy from your XW. I don't know if it's jealousy of your R with D7, or jealously of your R with your GF, or both, or even something else.
Since your mediation failed, has XW expressed what she wants in terms of custody or a parenting plan? Is there any logical next step? I'm not familiar with TN law, but can this current sitch just go on forever? I think having something finalized will give you some peace and help you with setting boundaries.
Me-47,XW-43 S13,S16 M:18 BD:4-23-17 W filed:7-17-17 (5 months of in-house separation hell) W moved out:1-6-18 D granted:2-15-18 Decree signed:3-29-18