Wow, good karma @
smontanaro . Do you think it is possible to roll the down tube dent out with blocks? If so, that would be what I would try first.
I don't mean that you have to do it. I wonder if a frame builder could do it.
I looked at your fliker pics and it may be tough to roll out. But it could be worth a try. Start on one end then the other. There is nothing to loose. Well, I suppose it could crimp the tube so bad that it cracks. But that tube doesn't look road ready anyway. Also Doug Fattic posted a splint type tube repair recently that once the tube is round again could return the tube to stronger than before condition.
I see you have a Serotta behind the J.P. Weigle. Good company.