When notice of the new documentary by Peter Michael Dowd appeared in my email box, I clicked on the link, scanned its contents, and summarily deleted the message about “Mr. Jimmy.” As someone suspicious of nostalgia and the squishy comforts it proffers, the last thing I wanted on my docket was a film about a middle-aged man who has spent the greater part of his life trying to recapture the heady buzz of adolescence.