Urgent help/advice wanted please?

Can someone help or advise me please? My dog - Prince will 13 next November. As a rescue dog, I took out insurance which proved beneficial as he developed skin problems not long after I had him. He had one toe amputated a few years ago and now has had a similar problem with toenail on one of his back paws which has bee removed, but now is very badly infected. The vet has suggested amputation of the toe, but I am worried because of his age. I´ve also been looking thing up on the Internet and found information on ´PEMPHIGUS VULGARIS´ which I wondered if this could be one reason for his condition now. Any help or information would be gratefully received as my dog is my ´baby´ as my children have left the ´nest´ so to speak. I had put this question on the ´DOG´ forum and was advised that it would be best to put it here. I do hope someone can advise/help me. Thank you.