Am I justified in my frustration?

He knew the diff was open to the elements, rain and such. He didn’t divulge that till I called him on it. I didn’t get that disclaimer.

He knew information that would put it in a negative light and went the other direction.

But had you inspected it, you would have known it. If it was as bad as you say...and I believe it from the pictures, it should have jumped right out at you. You obviously totally ignore inspecting it and now keep going and going and going. You had plenty of time to back out but you didn't.