CRF is a horrible condition, I hate it. I had to let my Midnight go last June after fighting CRF with her for two plus years. The vet came to the house to do the procedure. As difficult as it was, and still is, I couldn't bear the thought of not being with her and holding her and talking to her and telling her that I love her. I felt that I owed it to her to be with her as she crossed over the bridge for all of the love, affection and companionship that she gave me. I wanted her to pass peacefully in the comfort of her own home. I'm having a difficult time writing this...
I guess what I'm trying to say is that the deciding factor for me was seeing her quality of life diminish rapidly after her kidneys failed her. There will be feelings of guilt as you wonder if you could have tried this or done that but in the end you have to remember that despite our best efforts the condition is terminal. Midnight lived a good, active life for two years with the subq fluids and special diet and for that I'm very thankful. I miss her dearly and still feel the pain of losing her and still grieve for her. Human or beloved pet, it doesn't matter, that is the price that we pay for sharing unconditional love.
You have to decide for yourself what you want to do, no one can make such a personal decision for you.
Your decision to allow Otis to pass on peacefully is one done out love and it will allow him to keep his diginity. I'm so sorry that you had to make this decision.