Alex, I also have been fortunate to have very supportive family and friends (and lots of them) but I think the kind of 'move-on' advice we get is really about the concern that our support system has for us and the hurt we are experiencing. Also we have to remember that though our family members may love our spouse in their way, they are not in love with them the way we are. It may help to remind them of this. To tell them that you still very much love your W and after 18 yrs that you have a lot invested and want to do whatever you can to save this M. And that this is what you think is your best shot.
I do think you have it right that they are channelling their own anger at your W thru you. They are angry that she has inflicted this pain on you who they care for so much. And if you can do nothing, they can do even less than that to change this sitch.
When my sister said early on, "forget him, he's not worth it," I was upset b/c to me of course he was worth it and I thought it was cruel. But on reflection realized it was truly her anger and care for me she was expressing. She has overall been very much on my side. Actually she thinks my H must be gay b/c she can't for the life of her think of any other reason he would have walked out! LOL
I think as you get to a happier place, enjoying the life you create on your own, your family/friends will be more supportive of your choice b/c they will see less of the hurt that they want you to get behind you. So even though limbo might continue, you will look more okay to them. You will be more okay.
Seems like for many the idea of moving on means another R. Remind them that you are in no way ready for another R, do not want to bounce into a rebound thing so this is really a quieter way for you to grieve and heal anyhow.