Thanks so much for the tips and insight everyone.

I'm not about to give up on him (even if he does turn out to be psycho)...because I already promised him that this is his home and that he's definitely here to stay .

I've had many fur babies come to live with me over the years; after their behavior or natural traits became too much for others. Not one of them didn't adjust, settle down and become friendly in time. True, some did have their quirks, but who doesn't?

In fact, Willy the dog had spent nearly a year going from adoptive (2) and foster homes (also 2), as well as the SPCA before he came to live with me. He was tagged as potentially vicious, but he hasn't been aggressive without cause towards anyone since his initial adjustment period; and he's been a great friend, for 9 years now.
Oh sure, he needed a lot of understanding and some specialized training to channel his intensity away from aggression and toward play, but once he got that, he became more secure, and confidence won out over aggression.

I think that Ziggy just needs some time and some consistent, loving understanding...and there's plenty of that here .
I just hope that he hasn't been mistreated or abused along the way.
Still waiting to hear back from the Cat Rescue on that.

With love, Erika