For anyone that needs to hear this. You can't be reasonable with unreasonable people. Don't judge yourself by their standards. Do the right thing and focus what's under your control.

Set reasonable adult boundaries.

next he will shout at you

Full stop right here. Reasonable adults don't get a free pass yell at each other. We have the ability to use words to communicate with one another. If he's upset about something he can use his words to explain why, and you can discuss if there was desired or undesired offense.

So you set the boundary: "Dad, I love you, but I'm simply not willing to be yelled at by you anymore. It hurts me deeply. However, I'm absolutely willing to hear you out if I've upset you. I hope this goes both ways. These are signs of mutual respect. So going forward, if we're having a discussion and you start yelling at me, I'm going to remove myself from the situation, and when you're ready to engage again without yelling, I'll be there to listen to you. If we're on the phone, I'm simply going to hang up. If we're in person, I'm just going to leave. I don't want this to be the way we operate, but until we can communicate without yelling, it has to be this way."

and then give you the cold shoulder.

So when he's doing this use communications/plans that self-fulfill, meaning the communications/plans require no more action on your part after you've sent them. Example:

Don't use:

"Would you like to get lunch together tomorrow?" - Cold shouldering by him means you have to wait for his answer to act. He has power over you and your attention.

Instead use:

"I'm having lunch near X tomorrow. I'd be happy if you joined me. Let me know by 5pm today if you're interested in joining me tomorrow for lunch." - This way if he doesn't respond, his inaction is the response. You require nothing of him to go on with your plans. His actions or in-actions simply don't affect you.

It doesn't mean you don't have to keep working with him to grow up and be a functioning communicative adult. Its entirely possible he's too immature to have the kind of relationship you really want with him, but understand the alternative to healthy boundaries is you and your wife getting hurt by him on a regular basis. With healthy boundaries the negatives will shift from "hurt from him" to "disappointment in him".

💀

Don't suffer the bad times, you're an adult.

If he acts out, just say "ok seems like you need to deal with something. Cya later" and leave the house to do some other activity, or go home.

Providing him a free captive audience to act like a toddler is only reinforcing the pattern.

My in-laws can be like that in their own ways. Sometimes they're engaged with me and want to spend time, invite me to outings, and other times they're closed off, emotionally ambiguous and very off-putting. Unfortunately there's probably not much you can do about it without direct confrontation — but you may find that going that route can lead to large consequences, either good or bad. Might not be worth the gamble.

What can you do about it, that won't require a huge sacrifice or threat to your relationship? Just do everything you can to just be yourself, regardless of their mood. Don't coddle to their shifts in mood, but don't be hostile either. If they're being grouchy, don't play into it. It's challenging to not let the emotional sink of relatives mess your mood up but if you can learn to "float on top" of it instead of miring in it yourself, I feel like you'll see a lot of improvement in your everyday life.

Life is full of grouches and depressives. Sometimes a bit of distance, maybe even a bit of aloofness, can really help deaden the blows.

If he is being unreasonable, Fart and walk away. Keep doing that and he will eventually get the hint. Good luck bud !

Hang out when he's nice. Avoid when he's an ass. People can be temperamental, moody, an ass, or maybe mental (bipolar, for example).

He might be bi-polar? Regardless, you only need to show him the minimum socially required courtesies that is due to his position. I.e., to go visit him once in a while, ensure that everything is ok, to be courteous while speaking to him and to let him command the BBQ pit at his house. If you know something you'll do might trigger him, simply stop doing it. Say mmm hmm, yes, smile and nod a lot.