Tired of conflicts with dad. Any advice?

I suggest a discreet chat with his neurologist (if he's still registered with one since his previous stroke) or his PCP asking the practitioner to invite your father for a review. What you're describing suggests changes in his mental state which certainly want checking out, but it's clear that you'll get nowhere telling him you suspect him of losing his marbles and/or going round the twist - whereas if he's called in ostensibly as a matter of routine for his 3-year check-up he may agree to go.

Poor man. The sheer frustration of it, and how he must feel when he knows (and he must know) that he's lashing out at the people who do care about him. Keep your kid gloves on because he may be very depressed and very frightened and alone-feeling, but at the same time keep yourself at a safe distance. Taking the blocked loo as an example:
#1 not an emergency, he had two spares :)
#2 rather than offer a solution, ask what he would like you to do
#3 if his reply is negative - nothing! You're all useless! All plumbers are thieves! Why is the world against me! - then apply humor or sympathy according to taste. Just don't pick the battle if you don't need to.

Suppose he'd had only one loo and it had been an emergency: then you and DH visit, without discussion; you keep Dad busy in the kitchen while DH assesses the plumbing issue (or vice versa, if you're handier with a plumber's mushroom than he is); if it's a job for professionals you call in a trusted tradesperson and you give Dad the bill. Don't expect thanks but don't wait for permission either because it'll mean a month of arguing with no functioning toilet.

Hi Nugget, my SO is a service plumber. The guy your dad would call if you weren’t there. These people are so exhausting that he won’t even with them anymore, how he’s cheating them, the callbacks, all of it.

NUGGET3268, I read in your profile that your Dad has Alzheimer's/Dementia. That could explain why he was so upset that one toilet wasn't usable.... his mind had him thinking he was living in the past, in another house that had only one toilet. Have you noticed any other signs of "living in the past"?

If it is Alzheimer's/Dememtia knocking on his door, please remember your Dad has no control over this. It is just easier to agree with anything he says. And it is time where "therapeutic fibs" can be used. For example, I remember when my Mom [98] wanted to visit her parents, so I told her "they are visiting the old country" which my Mom accepted.

It might be coming closer to a time where your Dad might need Memory Care facility. But don't call it that, nor ever say "nursing home" because your Dad is of the age group that remembers when their own older relatives were placed in the County Asylum.

Your Dad may not know such newer places exist, which are now built like hotels, even having a menu style dining room. I know my Dad was quite surprised and couldn't wait to move in, as he was so tired of trying to maintain his single family house.

When dementia is involved, rational thinking & reasoning flies out the window. That's why your father is shaking & angry when a toilet is clogged and telling you that the last plumbing job lasted 'two weeks.' They get an idea stuck in their head & it can't be chopped out of there with an AXE. That's the nature of the beast, unfortunately. He's not purposely trying to be obtuse; it's his brain malfunctioning that's causing the issues. You won't be able to get through to him, unfortunately, because again, his brain prevents him from absorbing logic & reason. Living alone is a bad idea now b/c he's crossed over a line to where he needs help with activities of daily life; he shouldn't be dealing with clogged toilet bowls anymore. And the next issue could be leaving a pot on a red hot burner, God forbid, and burning the house down. Many people don't understand the danger of short term memory issues; they are the worst b/c an elder will forget things from moment to moment; ie: the steps required to cook or to take a shower, for instance. He can prepare a pot of food, turn the stove on, then forget why he's doing that, leave the room and boom, the food is burned and a fire is underway. Or turn the tub on for a bath, forget he did that, and a flood ensues. Short term memory loss is dangerously worrisome.

I suggest you read this 33 page booklet (which is a free download) which has THE best information ever about managing dementia and what to expect with an elder who's been diagnosed with it.

Understanding the Dementia Experience, by Jennifer Ghent-Fuller 
https://www.smashwords.com/books/view/210580

Here is a list of useful tips from her e-book I found to be excellent:

The “Dont's”
· Do not reason and argue
· Do not demand that they reason or problem-solve
· Do not demand that they remember
· Do not demand that they get their facts straight
· Do not correct their ideas or scold them
· Do not reorient them
· Do not think that they are being uncooperative on purpose
· Do not think that they really do remember, but are pretending not to
· Do not use a “bossy” dictatorial attitude in care
· Do not act with impatience

The Do's
· Enter into their frame of reality, or their 'world'
· Be aware of their mood or state of mind
· Use few words and simple phrases
· OR use no words, just friendly gestures and simple motions
· Do everything slowly
· Approach from the front
· Wait for a slow response
· Constantly reassure them that everything is 'OK'
· Keep people with dementia comfortable 'in the moment' - every moment
· Maximize use of remaining abilities
· Limit TV or radio programs which they may feel are frighteningly real
· Maintain privacy
· Provide a safe physical environment

Language Needs
· Use short words
· Use clear and simple sentences
· Speak slowly and calmly
· Questions should ask for a “yes” or “no” answer
· Talk about one thing at a time
· Talk about concrete things; not abstract ideas
· Use common phrases
· Always say what you are doing
· If they repeat their question, repeat your answer as you did the first time · Give them a longer time to process information
· Wait patiently for a response
· Be accepting of inappropriate answers and nonsense words
· Speak softly, soothingly and gently

Assisted Living is the logical choice now, or in home help if dad is resistant.

Wishing you the best of luck with a difficult situation.

Is your Dad willing to go into ALF?
You cannot act FOR him in this matter unless he is diagnosed as incompetent.
You may have to stop intervening when he has a problem. Your running over about the toilet got you no thanks and only angered him. Let him take care of things on his own, would be my advise and looks as though that is working for the brother.
I am sorry for his attitude, but as you say, he has always been this way, and it is just becoming worse.
Next time he calls about the toilet tell him you are sorry to hear that, and very thankful he has another to use; tell him you can direct him to a number to call for a plumber should he want one.
Again, it isn't up to you to decide on ALF unless Dad is incompetent and YOU are his POA.
Hoping Dad gets a bit more mellow and the toilets run clear!