I'd say this doesn't prove anything about anything. In fact, if he was abusing animals, or mistreating them, I'm sure we'd have heard about it by now . . . someone would have talked.
As for not leaving endowments, what about donations at the time? And as for selling animals . . . err . . . zoos and collectors do it all the time.
I do think its sad he never visited Bubbles, but its pointless to speculate about that now.
Like many things, we will probably never know the full story of his animals, and frankly, it doesn't matter now anyway. He's dead.