I was so sorry to hear about Dave. I don't believe I ever got to speak with him personally - well, no more than exchanging basic pleasantries - but, from reading all the messages here, it's evident he made an impact by assisting a lot of people, in their hour of need.
Although his life was short, he clearly thought it important to help others and succeeded in that. Therefore, his time was never wasted.
As someone has written above, an excellent way to honour his memory is to emulate his attitude to others.
My condolences to all his friends here.