I know exactly what you are going thru...this is what happened to my mercedes.
I can only tell you what my vet told me..and its not something you will want to hear..Mercedes did have good days..my vet told me to pick a "good day" to bring her in to be PTS. It was THE hardest decision I ever made...but she told me if it were her baby, she would not want to wait til it was a "have to" case..that is was kinder to say my good byes on a good day...where she had a lot of love, hugs and kisses and knew I was there.
Believe me it hurts my heart to even tell you this. I still have my days where I feel such guilt..because the day I chose she was getting along good..even ran around a bit..and I have to wonder how many more good days she might have had that I could have spent more time loving her. Those few days were far and few between..so many more bad days..and I know she was suffering. On those days she would whine non stop..even with me right there with her..because she just didn't know what was happening to her...she couldn't hear, could barely see any more..its just so unfair.

My heart aches for you...I hope you do have many more good days with Disney..and when the time is right, you will know it in your heart..just try not to beat yourself up over it, and that is easier said than done...hugs