It may be worth a trip to the vet. Sometimes things escalate if the "lesser" cat sees the older "king" is weaker or in ill health. After that's eliminated Try separating them both into smaller areas (bathrooms if you have to) and reintroduce them as if they are total strangers. It seems as if you believe the younger is starting things (I may be wrong, but since he's the one you talk of rehoming)....if that is true you could, next time you witness a fight, support the older one but noisily chasing off the younger and petting the old one. Sometimes, that gets the message that the old king may not be as strong...but he has powerful friends and order is restored.

The peeing is probably territorial and your husband is the male they both are "ranking" on....but eliminating the possibility of urinary tract problems or illness will help you know what you are dealing with. If nothing else, a mutual trip to the vet will make both of them smell different to each other and may set the restart process.

Good luck though, and try not to get too frustrated. There is a group (Cats International, I think) run by a woman named Betsy Lipscomb that has a website where you can ask questions and get suggestions too.