You can reference my old post(s) to understand the situation.
Backstory - about 15 years ago my FIL had some kind of an affair (no one really knows exactly what happened - at minimum it was an emotional affair. It wrecked my husband's family. My MIL got really sick, lost a bunch of weight, etc. My husband confronted his Dad about it, they didn't speak for weeks. Basically, the family was in turmoil. My husband doesn't know how his parents resolved the issue, but essentially, they moved on.
Well the "other woman" has come back into the picture. Apparently she called my FIL around Christmas time, I think she texted him. And as far as we can gather, my FIL and this woman have spoken since she reached out (we don't know for sure). My FIL decided to play a "funny trick" on my MIL last night, and pretended my husband was this other woman on the phone. Needless to say my husband was pissed that he was used in this dirty trick. My husband asked my FIL "Did you tell this other woman to buzz off and leave you alone." My FIL responded "No, not really." So.... we don't know if they are speaking or not. My husband didn't ask.
My husband eventually told his Dad something along the lines of "You better think about what you're doing. This destroyed Mom. And I can't believe you would entertain the idea of speaking with her and bringing her up. You should have told her to leave you alone." My FIL turned it back around on him saying "If you're really concerned about your Mom, you should know she more upset that your wife (me) isn't speaking with her." (See old post, I got into an argument with her back at Christmas because she was bringing up his ex-gf).
My husband flipped out. This is his Dad's MO. When he's confronted with his own mistakes (if you could call this situation a mistake), he flips the script and tries to make my husband feel guilty or like he's this awful son. My husband got off the phone and started yelling, he went outside and starting smashing firewood against our tress, etc. It was a mess. I don't condone his behavior, but this is so deeply rooted. Aside from the history with this other woman and the destruction it caused the family, he's been harboring so much resentment and anger towards his parents. They really weren't good to him growing up - there are too many examples to list but they basically turned their backs on him when he needed them most.
Of course I care about my ILs and their marriage but all of this is really none of my business. Still, after last night, the f*cking craziness and turmoil it's all caused, I don't know what to do. I insisted my husband start speaking with a therapist. He really needs to learn some strategies for dealing with them. He's carried this burden for far too long and it's destroying him (what happened last night is certainly not a common occurence but his emotions have boiled over more than once before). But when I'm faced with this, how am I supposed to handle it? I want to give him advice, and be there for him, but I don't want to convince him to make certain choices. I'm clearly a biased party in all this, I know the history and I know and love him. I'm just at a loss. And frankly, I'm angry at the toll this is taking on our relationship. His parents are a constant point of contention between us. Advice, please....