I completely understand that helpless feeling. Sadly, we all do including you. I'm so sorry for your loss of Henry. I went back into your old posts, and he must of passed many months after your last post about him in Apr of 2015.
Even though I'm married, I, alone, was forced to be the one to decide when to make that final loving decision for my girl...and back in 2014, I needed help.
The link below will take you to the incredible website I used when Jade was nearing the end of her life. Please don't panic, as I'm not saying in any way it's Oscar's time, I just want to share with you how helpful the page "Quality of Life" was in guiding me for exactly the right time in Jade's case. I can't remember but I may of mentioned when you were here last, that we did use their services. It was one of the best decisions I have ever made.
I hope it helps.
http://www.homepeteuthanasia.com/is-it-time/quality-of-life
Rebecca, hi, I remember you. I'm sorry to read your boy is so ill. You have a lot of kitties, who's sick? I don't have experience with liver failure either (Jade had kidney), just lending my support.
I'm so sorry to read about your boy, we're not vets here only pet parents unfortunately I don't know much about liver failure. If I find a good link I will add it later
I will ask though, have you checked closely on the label of the baby food to make very sure it doesn't have onions as one ingredient...many do and this I believe can cause liver failure in cats