You have done everything you could for your rabbits. Just some things can't be fixed. I've had a similar run of events and I'm now starting to bond my oldest (v grumpy but lonely) rescue boy with a rabbit we picked up last weekend. He lost several partners over the last couple of years, from various causes (longterm illness, death under anaesthetic, etc). I was going for a trio, but he doesn't get on with the other boy I got, so I've had to start again. Initial reactions look promising - they are OK sat near to each other through bars. The only thing is, this female rabbit turned out to be a neutered boy, so is also having a slight name change. I hope they bond easily, cos original bunny is a lot happier with company. Some bonds are easier than others - I'm hoping for easier... it will be nice to have him more settled again.
I hope it works out for you and Flo.