Motrin for dogs and how much exercise for 8-year-old mini- poodle with probable disk disease

Question
We let our male, neutered mini-poodle jump up on beds, run around like crazy with other dogs, do tricks (walking like a human etc.), and gave him 2-3 hour walks a day for years until our daughter was born. He is still very fit, typically has lots of energy, and he wants lots of stimulation, but his walks are down to 1 and 1/2 hours a day. Starting at age 5, he had a flare-up with his back and could barely walk for a couple days. The Vet said it was probably the beginning of degenerative disk disease. After recently turning 8, he had another flare-up for a few days after having a dog walker for 3 days in a row (1-2 hours of running with other dogs, I assume). He recovered again after two days of limping and not jumping up so much. So now, just a couple weeks later, we have brought him on our beach vacation and I guess the exercise of 4 hours on a beach wading the the water and an uphill hike of 2 miles was way too much for him. He is moaning and limping again. I assume we will have to get him stairs for the bed and try a better orthopedic bed for day time when we get home.

Is there a way we can gauge how much exercise he can have? If he gets too little, his behavior is not so good (chewing daughter's toys), but we don't want to overdo it anymore.

Also, is there Doggie Motrin? Can we give him a specified amount of human Motrin, calibrated for a dog--until we get home?

Any ideas on decent orthopedic dog beds?

Thanks so much for listening to this long email and for this great, free service!!!!!!

Answer
Motrin contains ibuprofen, very bad for dogs.  You should be able to pick up some aspirin, buffered is best.  5mg per pound of dog every 12 hours.  Baby aspirin may be easier to dose.  Adult has 325 mg per tablet, just right for a 65 pound dog.   

It is hard to say on the exercise, just trial and error once he sees the vet and is feeling better.