RE: Having Problem with sight picture When Bench Resting
You may want to try a pair of glasses with the non shooting eye side covered with a bit of milky scotch tape. It allows the other eye to stay open but not trying to focus. And if you cover it with something dark the non shooting eye will dilate to make up for the missing light and cause the shooting eye to also dilate since the eyes are a pair and sympathetic to each other.
I'm also 40 and my iron sight vision is like your scope vision. I can't stay focuse for long. So I try to alternate somewhat quickly. IE if the shot won't go right away(thats the best thing to happen and if you practice shooting quickly you'll realize that its as good or better than shooting slowly, as long as you do it right and don't miss condition switches) I'll blink and look off for a split second and then look at it again and try it over.
Also as mentioned nutrition is super important. Before the prone slow stages that start at 600 yards with iron sights that I shoot, I need a boost of sugar. But natural sugar is much better than a candy bar etc.... I've taken to drinking 100% juice cut 50% with water and eating a fair amount of applesauce about 5-10 min before shooting. Helps extend my vision quite a bit.
Don't worry about your trigger weight. You are used to it. I've hunted and shot a lot. I'm extremely used to different triggers. The key is to remember I'm not touching my trigger till I'm good. Then it doesn't matter how heavy or light. I've hunted with triggers under 5 oz and triggers over 7 pounds. Never had an incident. And as long as you follow the rules you'll be fine too.
Jeff