Welcome to this side of the forum but I'm sorry that your dad seems to be having issues :(
This forum doesn't get much traffic but if you are looking for a specialist, go to ratemds.com This is a peer based website that gives reviews on doctors by speciality and location.
Actually Alzheimer's is not too difficult to diagnose but unfortunately when the symptoms are strong enough to warrant an evaluation, the disease has progressed. But, yes....early treatment MAY slow down progression. The key is finding the right treatment.
Best of luck with your father and if you have anymore questions don't hesitate to ask.
Moderator-Allergies/Asthma, Alzheimer's, IBS, Co-moderator-UC
Diagnosed Left sided UC '92 - meds: Apriso, Remicade) Unable to tolerate MOST mesalamines* Currently in Remission, IBS, Diverticuliar Disease, Fibro, Sacroiilitis, Raynauds, OA, PA, Rosacea, Psoriasis, Dry eye syndrome and allergies controlled by Zyrtec