I am sorry to hear that Totti is struggling more now
I know what it is like having to constantly try to assess quality of life and to question ourselves constantly about getting it right. I now rely totally on my Vet with regards to 'the decision', I know she will always make a judgement in the best interests of the Rabbit. I always hope I will too, but I also always have that bit of doubt that I may get it wrong.
Maybe have a long chat with the Vet who knows Totti best and the Vet that you trust ?
Lots of noserubs to brave Totti