First of all... take a deep breath...
Now, do this, step by step:
1-As I said before, if Doyle is with you, go to sleep in the evening, he will leave.
2-Next morning (or afternoon or really any time) go the the basement, if you don't see doyle's ghost on the right, talk to the bones, it will play the first aparition scene, and he will enter your body again. (This triggers the the full ghost mode).
3- Go to sleep again in the evening, he will leave you, again...
4- Next morning, go to the basement, again, and this time, Doyle should be already in ghost form on the right of the map.
5- Talk to him, if you already talked to the merchant and the MC said something about needing Doyle's help, once he possess you, the dialogue about the attic and the item to sell (and the ring) should trigger.
If this does not work for you for some reason... just give me your savefile and I will fix it for you.
Now, breath again, think of happy thoughts, we are here for you, you are loved and deserve happiness.