Sounds like you need to do some soul-searching and decide whether you want to save the M or not. It sounds like you're not sure.
Even though your sitch has been going on for quite a while, you've only been S for 5 weeks. S can change the dynamics quite a bit. Once W is out on her own she may very likely discover that the fantastic, perfectly happy life she was imagining is not really reality. And if she is continuing the R with OM, at some point she'll discover that that too is not the nirvana she had pictured. This realization can take many months, but once she gets there she may very well find herself missing you and finally appreciating all the changes you've made.
So you've got to decide whether or not you're willing to wait it out.
