I actually got one back to its owner. The other I could not find as it had ran off.

I live in the U.S.

I'm not exactly sure. I'm new to Rottweilers hence the question, but I have read that Rottweilers specifically have hip and joint problems. Honestly if anyone can say factually it's a duplicate then you can close it.

Fleas exoskeleton is hard im not sure why the reference itself said it is soft. Im not sure if the soap is strong enough to dissolve the hard exoskeleton or not . However the exoskeleton doesn't cover the head of the flea so it is possible it dissolves or coats the head and kills it.

It seems i have been slightly mislead. It seems that formaldehyde kills bacteria and fungus and although some sites say it kills fleas they didn't properly cite any references so I will assume I am wrong in that part. However that being said dawn does kill fleas but in a different way. I will edit the answer with links and a better explanation to this.

Soap itself does not kill fleas, however the Formaldehyde inside dawn is what kills the fleas. Dawn has such a small amount it is perfectly safe for animals although it is deadly for fleas. As I see from the answer you looked at that the idea was that dawn drowns the fleas. I can assure you it is Formaldehyde that kills them and in some cases attracts them resulting in their deaths.