Hi,
Your story is mine; except that I'm the wife of a husband with a father just like your FIL. And my husband is an alcoholic (his way of coping with the fact that he's the child (one of 3 kids) who caters to the needs of a dysfunctional father and mother).
My anger at AH's family was (and still is I supposed) intense. I fully understand the frustration of walking around the elephant in the room, being expected to cater to the needs of someone who is sucking the life out of all around him and resenting what it does to your own family.
My only suggestion is for you to detach from her family. Chances are this will cause more strain and I imagine that you will always be the bad guy in her family's eyes bc you will be the one unwilling to play the enabling game. When I stepped back and stopped enabling my MIL and FIL along with my H, it made things worse between he and I.
We are now separated (for many reasons) and he is still addicted to his family and is getting dragged down with them.
My FIL and AH are both charming (at times), excessively manipulative and demanding and will take and take and take for as long as people are willing to give. Setting limits with either of them sets off a storm of fury and I've been blamed for all that is wrong with AH's family and my own family bc I stopped playing enabler. It hurts, it sucks and it's inevitable.
I had to decide finally that it was either me and our kids or AH and his family. I thought that all of us could co-exist and be healthy/happy and tried to make it work and it didn't and never will. Alcoholics take hostages and your wife and you are hostage to her father.
You can't wait for your wife to agree that you don't want to visit her father anymore. Just tell her you won't visit him. You have that right.
If he's in assisted living, why do you guys have to take him to the emergency room? The more you can step back, not interact with him, deal with his problems or try to make him change, the happier you'll be.
Just be prepared for guilt, blame, probably anger from your wife... But from the experience of someone who tried this for 8 yrs, I can tell you that nothing but detachment (emotional and physical) is going to keep you sane.
I really hope your marriage survives this. There's nothing more toxic than a child of an alcoholic who can't see how enmeshed they are with their family of origin (I guess it's no different than being a spouse of an alcoholic and being enmeshed too). Long before my H's drinking took off, his sick enmeshment with his mom and dad caused a crater sized divide between us and fractured our marriage beyond repair years ago.
I hope you have a happier ending.