Thanks
@Brunneria
It is difficult to deal with the watching this in slow motion inspite of the best medical care available to us.
Even more so after I have discovered how easily much of this could all have been avoided...
Whilst I can't imagine what you must be going through, and how you feel about your own discoveries (in terms of prevention), all you can do for your Dad is deal with the here and now, and help him through the future.
For a time, it looked we would be facing the prospect of my Mother losing a leg (not diabetes related) as her circulation teetered on the edges of viable. I'm delighted to say on that account, she struck a line of excellent fortune, and we were all spared it. I know it was a terrifying prospect and I am eternally grateful we got the lucky break.
Not all situations are avoidable, and perhaps your Father would have had poor circulation, even without his diabetes. Just a few short years ago, things weren't so well understood, and folks of our parents era are far more likely to have treated their Doctors' words as unquestionable. Nor, of course, did they have the massive benefit of the internet to aid their research.
I really do hope your Dad copes well with it all and will recover to enjoy life again.