Gabriel, I would just accept what she says re her work. If you start making comments about how you don't want S5 to go to Summer Camp, she might view this as more of the same critizing her mothering.
However, on the babysitting front, only do it if it doesn't make you feel used. Also another thing to think about is, if she wants to be independent (and do her own GAL by the sounds of things) then relying on you to care for him is not exactly independent. She is not having a chance to experience true 'single' motherhood and therefore the incentive for taking you back is less.
If you can agree to have S5 in a way that nurtures your R with him as well as helping your R with W, that would be best all round, just look out for yourself too and make sure you don't feel taken for granted.
It was good that your W liked the present you sent her, though. That's a good sign.
