General 10m rifle questions

[Graemevw]

Been playing with my original 75 again today and it's thrown up a couple of questions. All unrelated, all probably pretty simple.

First off, point of aim. I shoot bell and 6 yard but also have some 10m 5 spot cards. Thought I'd try one today, see how much harder it is (37 out of 50, not much worse than my 5 yard scores today!)
I noticed though that my shots were going high. I didn't adjust the sights. I expected drop. I guess this means the pellet is still rising at that distance or maybe I'm shooting upwards. What should the height of the center bull be?

Secondly, my anschutz adjustable iris doesn't quite fit nicely on either of my diopters (original 75 diopter and diana 82 diopter). I only need a little more distance. I could make a small spacer so it doesn't screw into the diopter as far but that seems a little like a bodge. Are there extensions available to space the rear iris away from the diopter?

Thirdly, I'm a bit sick of element inserts so have been looking at adjustable front elements as I can't settle on one size that works for bell and paper targets.
The issue is, my original 75 has a stupid front sight so nothing is going to screw into it. The original sight slips over the barrel and is held by a roll pin.
My plan is to make a new one (or modify one if anyone has an original 75 front sight for sale). Then I can cut dove tails into it and fit a new front sight.
If I can find a spare 75 sight I might even be able to bore it out and tap it m18 x 0.5.
If I do the dovetail thing, what sizes are they normally? I see you buy front sights for your specific make. But I can't find any info on what makes have what size dovetails.
Old anschutz front sights seem plentiful, might make sense to make them whatever size they are.

Edit to add one more query if I may.
I've been trying to get my head around this staring target shooting thing for about 5 or 6 weeks now. I'm starting to feel it in my back a little. I wouldn't say it's pain yet, just a niggling beginning of an ache. 5 years ago I had spinal surgery for a badly ruptured disc that I'd lived with for 20 years!
As im only really shooting at home and a bit of bell target at the club I don't really want to go down the road of shooting jackets. Has anyone tried any kind of back support? The usual neoprene wrap around type thing.

Thanks.