That setup worries me to look at. I was racing and working in bike shops when the Super Record parts first showed up, so I'm very familiar with the limitations of that derailleur.
It's not a Suntour or other slant-parallelogram design. Please forget about the modern mania for making sure that all possible gear combinations are available. With your setup, they can't be. No kidding. Here's why:
The Super Record is just a refined version of the earlier Campagnolo designs, e.g., the Sportsman. Look in the racer's bible from the 1950s and 1960s, the so-called "Cinelli book," to see how such derailleurs were originally intended to be used. My copy includes an illustration of the correct shifting method: there's a four-sprocket straight block with two chainrings, where dotted lines indicate that the inner two sprockets are to be used with the inner (47-tooth) chainring and the outer two with the outer (50-tooth) chainring. Two chainrings, four sprockets, close ratios, four allowable combinations.
If I were to try using a triple crankset with your derailleur and freewheel, I'd train myself to use the inner three sprockets with the small ring, the middle three (including the third largest sprocket, if that's one of the middle three) with the middle chainring, and the outer three (again including the next largest sprocket if appropriate) with the big ring.
I'd also cut the chain such that it sagged in some of the gear combinations that you want to try to salvage, because riding with a sagging chain might be unsightly, but it won't wreck your derailleur. Or the dropout. Or the spokes, should the derailleur do a kamikaze dive into the wheel. That painfully stretched derailleur may work fine on the work stand, but on the road, under load . . . . .
Last edited by Trakhak; 07-09-20 at 07:49 PM.