About the eyes; I was in the same boat as you before I had cataract surgery, I bought a Kibler SMR kit, put it together and found with the standard sight placement the rear sight was just a blur so I sold it.
I had built 4 other flintlocks and always put the rear sight WAY down the barrel, on these guns the rear sight still wasn't clear but I could see it enough to shoot.
One day i was out in my shop tinkering and thought I would make a simple peep sight for my #1 deer rifle. After a whole day of cutting, filing and bending I had a peep I could try out.
I started with this;
View attachment 324281
And ended up with this;
View attachment 324282
When I shot my rifle with this peep if felt like I was cheating, the sights and the target were as clear a bell, I hadn't seen a clear rear sight in over 20 years.
You can buy these tang mounted peeps, the commercial ones look a lot better than what I hacked out. This may correct you vision problem.
I have had cataract surgery since I made my peep and can see my sights now.