Steve, bless you and your Benny. Your post brought tears to my eyes. I understand that pain so well. Please don't try to second-guess your decision, you made the decision from love as we all do when we have to. Often said - better a week too soon than a day too late. Also often said is how dogs are stoic and hide their pain so what you see might not be what is going on underneath and how bad it is for them. I know with all of mine when they felt unwell they stuck close by to me - you said that Benny did this too. Maybe it's comfort / security, I don't know but think when I feel ill I just want my mum to be around, I sense it's the same thing.
For me it's nearly 3 week and I am still struggling badly. I don't cry and sob so much as I did those first few days but worse is a deep-rooted sadness and sense / knowledge that life has changed forever and I find that is the hardest thing. Emptiness. My house feels too big. I am so sorry for your loss and I feel and share your pain. I find comfort here being amongst people who understand.
Zippy 13/01/2008, Button 06/01/2016, Jake 11/05/2016