He probably knew that your home was not his home, but with the wheelchair ramp, he figured that your family must be similar to his. He knew you would help him, and you did!
I don't think I could accept reward money for returning a furbaby either, even though I could really use it.
I want a rescued greyhound, but the Mothership says, "no more pets!". I am usually terrified of big dogs (I'm really small and some of those big dogs are bigger than me). But greyhounds are so sweet and quiet and loving. They don't act like the full-grown labrador who thinks he's a lapdog!