I have seen people on here say that it has helped them in situations like yours to think of their S as a nice stranger: that's how they treat them - friendly but without being overly connected and familiar and by keeping their guard up slightly to minimise the hurt. Using caution and being careful about the details they divulged.
I read what you say about keeping the door open....but I wouldn't be too frank to your H's face about that otherwise he will just think you are happy to sit there waiting until he pleases to come home. I really wouldn't tell him one way or another about waiting.....why should you? You can show by your actions what your intentions are...however I would say that being TOO available will probably make your H complacent about sorting out the sitch.
My H would have loved for me to have given him time to decide who he wanted to be with....he did ask for that. I am afraid I just said no; as far as I was concerned, if I let him start thinking he had whatever time he needed to make a decision then what incentive was there to decide? It must be great to be fought over and the object of two people's affections. There was no way I was going to butter his ego up the way he was behaving. OW was feeding him enough B*llsh!t like that.....and he KNEW it was just an ego trip and wouldn't last and that really she wasn't being honest. I didn't have to be nasty about it but I did have to be firm and consistent. I made sure he knew how much he meant to me and the children, I validated his feelings as to why things had gone wrong, I owned up to my share in the M breakdown that led to the A...but as for enabling the A to continue once I knew about it....well that was a no no for me- it was a boundary I would not cross.
Saffie me 46 H 46 M in 1986 D20,D18,S16,D13 H's A 01/05 to 07/06 H recommitted to M 07/06 renewed vows 09/06 Going from strength to strength