Sorry for your loss, man. Poor do. That's a long half-life, although the half-life of diazepam can be up to a couple of hundred hours plus, once it's built up. I know flubromazepam is somewhat more potent than diazepam (which is a fairly 'mild benzo', in the grand scheme of things), however. It's one thing having 10mg of diazepam with something like codeine, but heroin and untested benzos sounds damn risky. This is the sort of shit that prohibition causes.
I have had flubromazepam, and didn't have any issues, but I didn't take the piss with it.