NEVER, EVER, think that you let Bob down. You and your hubby were "Angels" sent to him, to make his lasting days full of love and comfort. You did more for him than anyone else would have. You are helping him ease his way to Rainbow Bridge rather than die in a cold cage, alone.
I know this is so hard on you guys, but know that we are all behind you 100%.
My prayers and thoughts will be with you and Bob tomorrow.