My husband & I have been married for 57 years - we were high school sweethearts!! He also has similar problems except that he has been diagnosed with Lewy Body Dementia - (which means in addition to memory problems, he "sees things, people, animals that are very real to him_ --- like your husband, - this has been coming on for several years - (since we both had Covid Feb 2020 - we both think it was brought on by Covid but Drs just ignore our idea - Feb 2020 was before testing - before shutdown - before we, the public, knew much about Covid!)
The memory issue was the first thing I & our daughter & son noticed - all of sudden, he couldn't remember how to play cards (500 - & Rook card games -- & he was a good card player) He had trouble golfing, then his eye sight was bad - he had to have surgery for Stramisbus (lazy eye) - he couldn't drive as he was seeing double! His hearing in right ear has always been poor, we've had 3 different hearing aids (all more costly than the last) but his hearing just kept getting worse -(which also contributes to Dementia because it cuts off information brought into the brain by hearing) --- we've finally been able to find a neurologist through Mayo clinic in Rochester, MN who prescribed a PET scan, which confirmed the diagnosis of Lewy Body Dementia. (Hard diagnosis as Drs/research still don't know what caused it or how to stop the progression)
However, there has been some hope - Dr Botha (Mayo Clinic Neurologist) affirms that HEALTHY DIET (Mediterranean Diet with emphasis on GREENS, FISH, CHICKEN, NUTS) EXERCISE - (to make your heart work - weights, balance, walking 1/2 hr/day), WATER HYDRATION, & STAYING SOCIAL will do the most to combat the progression. (having said that - my husband argues that exercise can be vacuuming, lawn chores, etc. -- but Dr Botha suggested he think of Diet, Exercise, Hydration, Socialization are prescriptions - drugs, that will help slow the progression. (My husband takes Aircept, which is a Dementia drug that is supposed to make hallucinations less bothersome (?) - he's been on High Blood Pressure meds for years, & he takes potassium, & daily Vitamin.) He also have been approved for a Cochlear Implant in right ear - the Surgeon (Mayo Clinic) assures us that any help the brain can get to bring information into the brain, will be advantageous!!)

I too, run the gamut of patience, frustration & then angry outbursts at my husband, or at the whole diagnosis. (I have bouts where I'm angry at God for not taking this away - my husband has been a patient, Jesus trusting believer his whole life -- so I question why God doesn't take this away. But I too, Believe Jesus died for me & I hold on to that fact when I am angry!!) ( and of course the people in Ukraine, Russia, Israel, Gaza, & many countries across the world, suffer much more than we do!!)
We rec'd the March 2024 AARP Bulletin - "THE FUTURE OF ALZHEIMER'S" -- that too, gives us hope! If you haven't read it - get a copy - it helps to know "they" are finding ways to combat Dementia/Alzheimer's - and the myriad of diseases that can cause it!