Just reading back through your thread again...
Whatever was causing Bob to be unwell was clearly at a very advanced stage and had been going on for some time. You'll probably wonder what might've happened if you'd not started the heart med and had waited for a referral to the Uni Vets instead. In this situation it's natural to wonder about the "what ifs". That shows how much you care. But I really doubt if that referral would've made a difference. You probably would've had to wait for an appointment, whilst leaving the condition untreated, and by then it may well have been too late.
The truth is, you'll never know what would've happened if you'd waited, so please don't dwell on it. If it's any consolation, if I was in your position I would've probably done the same and tried the meds. He was very ill and you did your very best, in a terribly difficult situation. Most owners wouldn't have gone to the lengths you did, in trying to find the right help, so he was lucky to have had you caring for him, keeping on seeking answers and not giving up x