The ruler's just to make sure the top tube and/or down-tube aren't bent - you can do that yourself, using the straight edge of the ruler as a reference point any bend will be clear. You can use your fingertips to check for bulges - gently stroke all around these two tubes from about a half inch to five inches behind the head tube. If a lightweight frame takes a really heavy frontal impact, the thin tubing can slightly telescope where it absorbs the energy, causing it to thicken at that point, creating permanent damage. It's hard to describe, but your fingertips will definitely feel a bulge if this has happened. If not, great!
I really couldn't tell from the photos, but they looked OK as far as I could see. Also, in the photos your fork legs definitely look bent back behind the fork crown - but might not be. Your Colnago/De Rosa expert will tell at a glance and it's likely your LBS man did too, when he told you it was OK. If the fork legs are bent back, it might not mean a new set of forks - a competent frame builder will be able to braze in a replacement steerer tube if that is bent or might even be able to re-set the legs - but get a quote first - craftsmanship quite rightly costs money and it might be more economic to replace them if that's necessary. As far as the rest of the bike goes, I'm with the other members - strip it, clean it really thoroughly, adjust and re lubricate every part and a bike of this quality will run like new. Only replace worn parts - I'd say your chain and sprockets are most likely due - but keep the rest adjusted and lubed - it'll last for years!