Blimey edz, I take a day away from the boards and all sorts of things happen....
Glad you had a good time with S at the science centre and that you had a nice family day.
As for the conversation with your wife, I can see lots of positives there and from your descripition I think you handled it really well. As others have said she must be seeing your improved R with S.
The one thing I would say to remember is that when you start dating (anyone not specifically now) you dont leap into full marriage living together territory. I sometimes feel that we are looking for full 100% recommitment when actually starting to date again (beginners mindset) may be a more realistic prospect.
As for the 'thing', i would say dont dismiss it but concentrate on the reality of what is happening with W. if you do think of it use it as a way to keep your expectations under control
Hope you have a good day
Both mid 30s, 2 young kids BD 7sep14 XW moved on long ago, now living with OM1 D paperwork in progress