Susan, it is good to hear from you and know that Fainly seems to be doing fairly well overall. The cone is so important, as you know, to keep him from his surgery area ...my Sketchie had to have a cone for weeks after his leg amputation and although he hated it for the first couple of days he got used to it and it really wasn't an issue. With no exercise, which is critical to stick to for Fainly, I am not surprised his food intake is substantially down and as long as he is not losing weight I honestly wouldn't worry about it. In fact, if he was still eating what he ate when he was more active he would gain weight and that is the last thing you want as it would only add pressure on his legs once he can be up and about.
Does Fainly like to ride in the car? If he does and is either seat belted or crated, so he can't move about, you might find it would cheer him up a bit...just make sure he is securely limited from any real movement.
I also wonder if there is still some level of pain associated with the surgery...it was by necessity a very invasive surgery. Maybe talk to your vet about extending limited pain meds for a little while longer?
Gentle hugs to your big boy...he and you will get through this and in the end it will have been worth all the worry.
Trini