Those are pretty small pictures aren't they, couldn't you have taken a bit more of a wider shot and posted larger ones? I know you maybe touchy about pictures
but it would help
Anyway, going by your first pic, as you say it seems to only have been pushed back by an inch at best. When we took delivery of our car, our bumper was pushed back by a similar distance and it took them less than 15 minutes to realign it. I'm assuming there aren't too many bolts that need slackening to adjust it. I seriously doubt that there would be any further damage behind the bumper, as it's name says it all really and it would be stupid to put something so close behind it that may become damaged
I have taken the rear bumper off my 156 and there is plenty of space behind it. I should imagine it's the same for the front.
Can't make heads or tails of your second piccy
As for the people saying that they need to take it off to assess damage.. well maybe they are being careful as not to under quote, although I normally am very scepticle when I hear those words. Better still, ask them how much would it cost if only the bumper is damaged. Also, if they find any subsequent damage, ask that you would like to make the decision if that require repair, as it may only be cosmetic and hidden after the bumper is repaired.
BTW - maybe a good dent fixer wouldn't even need to take the bumber off. That providing that they fix dings in bumpers too
So as long as the damage is repaired on the cheap, you may well be able to re-align the bumper yourself
Dunno if that helps