Thank you for your excellent, well-reasoned, and balanced post. Along with many others, I think the chances of invalidating the patents at trial were minimal --- however, and as another example of what I was talking about in responding to Dys yesterday, this is the type of analysis that lawyers must go through when deciding whether to actually go to trial or not. I don't know whether I would go so far as to say that it was TPL that didn't want to go to court, but I do think it is virtually certain that the settlements took into account the factors you have mentioned, along with many others --- as I have said before, most litigation is merely risk management.
I can advise from personal experience that when you're in the "judicial trenches" and are faced with the possibility, even a relatively small one, of an "all or nothing" outcome, there are few absolutes and lots more shades of gray. It seems to me that this would be magnified when the outcome might also affect future cases that are being contemplated, and/or existing and future settlement demands directed at other companies.
Best wishes.