I reread my post and I painted her harshly (again). I think W is very loving to S5, and we just need to finesse how/when she can vent about parenting frustrations. W is tired and stressed, but I doubt she'd ever purposefully be mean or cruel to S5.
I've found that when I remind him about how much she loves him within earshot of her, she softens and seems to release a good part of her pent-up anger. I know its not my job to regulate her emotion, as she's an adult who does that pretty well already. However, as Jo, Wes, UD and others have pointed out, S5's the glue that holds us together in some sense of an R, and I need to respect her mothering as much as I can, even if its different from my version of parenting.
When I called S5 to say g'night, W answered and was pleasant, and asked "Where are you?" (usually she just calls my cell phone, as location doesn't matter then). She asked to call back as S5 was in the tub, and made the call herself later on (S5 knows how to call me himself). Her voice was more relaxed, even pleasant. S5 pointed out that W called me each time, and I asked him to thank her for doing that.
Hopefully, the rollercoaster is heading up...
This weeks goals:
1) Absolutely no defending of myself - listen & validate only!