I'm not ashamed to say I was in Ladies Wear most of this morning, however at the time I was rebuilding one of the tills at House of Fraser, and that was the department it was in... 
Men's fashion has been the same for years, only now are we seeing a change (see Kanye West... okay perhaps not the best example), but searching 'manskirt' will bring up a lot on Google. Designers, encouraged by popular figures in entertainment have caused this, even Jamaican Dancehall singer Elephant Man has joined the fray, and then of course the guy from Rough Copy (last year's X Factor) who was always in a skirt of some sort, albeit with thick tights or leggings... Aside from kilts or shorts, a man's wardrobe is quite limited, so perhaps your DH was curious. The jacking off is a step too far, and he needs to replace what he damaged (the dress, shoes, tights).
Casually ask him if he'd like to go shopping with you and see if there's anything he would like for himself - that will shock him. Or fit CCTV web cams in every room bar the toilet, and just say 'the police fitted it as part of a crime reduction initiative in partnership with the local council' if he asks...
and watch him from your phone or laptop when at your next conference. 
He can't skirt the issue forever...
and he will have to discuss it somehow. There is a way of retrieving erased stuff from an iPad if you google it. Do you share an Apple account?
Who's he sending upskirt pics to?
have you asked your DCs or were they elsewhere when this happened?