Look into dihexa. It’s not without risk but is 7 orders of magnitude more effective at crossing the blood brain barrier than current drugs on market. It’s passed through safety clinical trials and is moving to efficacy trials now under another name fosgonimeton. I take it myself due to severe ptsd related memory problems and it has been amazing for retention/learning/anxiety. Needs to be put in DMSO and applied topically (I use my forearm). Orally works too but much lower bioavailability. You can get it through research chemical sites or through hormone/anti aging doctors via compounding pharmacies. The compounding pharmacies are not cheap though, the cream is like $750. From research chemical sites it’s more like $100 plus buying your own DMSO for like $20.

I realize you weren’t looking for this advice but maybe it’s helpful? Good luck with your dad.