Thanks, Izancai! ^^ I've studied genetics a great deal for my own interest, and I used to play around with this sort of thing for fun (creating animals with specific genetics and then crossing them). At one point I had a 'herd' of about 130 fictional horses, every one with a drawing, pedigree and genetic blueprint. Yes, I had a lot of free time when I was younger.

From the descriptions, I'm guessing your boy and Jayden would be Aat/BB/mm and Aat/bb/Mm, so you're right: no chance of any red puppies there. All the pups will carry red though, because they'll all be Bb.
Merle is the same gene in Great Danes as it is in border collies (as well as all merled herding breeds and dachshunds), so it unfortunately can produce double merles with all the same problems if two merles are bred together. The odd thing with the Danes is that merle can hide in the harlequins, so non-merled parents can have merle puppies. o.O It's due to the Harlequin gene overpowering Merle, so the parents might genetically both be merles but look like regular Harlequins. Their merled pups don't have the dominant Harlequin gene and can produce double merles with other merles. On rare occasion, double merles can be born from two Harlequins as well if they don't get the Harlequin gene from either parent. It's too bad merle isn't an accepted colour in Danes, because it occurs often and looks amazing on them.
Merle Dane puppy