Is dog cephalexin the same as human cephalexin?

Yes, exact same thing. Most vets will nickle & dime you and dispense the medicine at their clinic. However, purchasing antibiotics with a RX from your vet at a human pharmacy is much cheaper...

yes

Very possibly. Cephalexin is not FDA approved for canines, but is often given as an "extra-label" med. Typical dosing is 10-15 mg/lb, tid or bid (2 or three times a day). Be advised this is a...

Uhhh...yes, other than being from a dog...

no. dogs hearts beat faster