I'd let the gloves dry slowly and naturally away from sunlight and any source of heat whilst laying them flat.

Not necessarily. A lot of this is personal preference of course, so please take this with that large caveat in mind, but I'd rather suffer through a longer break-in period to loosen the cuff and glove interface than to permanently accept and live with a looser fitting glove. Blood circulation around the cuff, and therefore to the hand, will certainly be immediately better with the larger glove, but the looser hand fit to begin with will only get looser still in the long run as the gloves break in.

As the saying goes, there's nothing more important to going faster on two wheels than front-end feel. The higher the front-end feel, the higher your confidence will be. I think a loose-fitting glove where my hands are swimming in would make me feel very nervous. And Dainese gloves, as you know, have beautifully sculpted palms that transmit an immense range of sensitivity.

Breaking in that cuff / gauntlet interface can be time consuming, but short-cuts exist. Again, please insert HUGE caveat here. Rub in some leather conditioner around the cuff / gauntlet (Langlitz brand is the best; use your fingers to rub in for warmth), then basically put your jacket and gloves on, cinch down the hook-and-loop gauntlet to a comfortable degree, and then, well, basically do some household chores in between random pushups. No joke. You'll look a bit of a dork frankly but you'll feel great and the payoff is awesome - an upper body workout, a little cardio running around the house dressed like a power ranger, resulting in soft supple leather slowly but surely molding to the shapes of your arms and wrists. Wouldn't even dream of offering that one up if I hadn't actually done this a few times, much to my shame.