Yes, it is all so hard. Having had to deal with this with my mother (who ended up with full on dementia, nursing home placement and she passed a year ago) to now having to start all over with my spouse (very early MCI); at least this time I have a clue. So glad you have a therapist! I have been working with a great therapist for 4 years now; it really helps to have a "safe space" to off load all the emotion and to be heard without betting down family and friends with this.

Perhaps audio books are better, or "Ted Talks" short and interesting; and you pick simpler things. Also, the trying to explain things is just a source of frustration for you both. Try as best you can to divert to something else, or try to say I do not know and walk away. My mom was hard of hearing -- refused hearing aides -- when she'd get into such a loop; I'd say "oh, my cell phone is ringing and it is in the other room." That gave me a reason to "walk away for a bit." My mom, lived with us so it was a 24/7 thing until a nursing home placement had to be made for her care and for my sanity.

Having an aide (maybe a buddy, friend aka aide) come a few times a week to give you respite can help too. Go out with friends, talk a walk, go to the movies; anything to take a break if you can.

Sadly, preparing for what comes next with a licensed elder care attorney is a good idea. Get all the paper work, documents, account details (online things too); so you can step in and take over when the time comes.

Best of luck, take care of yourself. Ask friends and family for help when needed. Hire help too. Nothing prepares anyone for this, so do not beat yourself up when hard decisions have to be made. Hugs