First, you replace the Mini's rear sight with a TechSight Mini200 and get the $15 option for a replacement post into which you can add one of the 3 size apertures. Then you insert the smallest, .042" diameter hooded aperture. It will look like this when done.
Another advantage of the Mini200 rear sight is that it moves the rear aperture 1/2" back making it easier to get your eye closer to the sight that, coupled with looking through the small aperture, increases the Depth of Field (DoF) which is the distance from you eye that everything is in focus. On my Mini, the DoF effect makes it so that both the front sight and the target (be it 25yds or 300yds) are both in focus.
Then you address the front sight as the NM sights are thinner than stock. You need to thin the front blade down from it's .075-.077" thickness to .050" by carefully filing one side down by 1/2 the extra thickness (about .012-.013") using the other, untouched side as your reference plane. Only when finished with the first side do you start on the other side. You then file it down until you're to the desired blade thickness. That way the blade remains centered in the sight. (Note: I first thinned the stock front sight. When I added the new front sight/FH, I thinned that blade as well.)
Based on the shorter 18.5" barrel, your new sights a equivalent to the .052" rear and .062" front blade of the NM sights on my M1A.
As to your sling issues, I have seen some add a couple of swivels to the side of the stock so that the sling lays flat on the side. I learned how to sling a rifle on my shoulder in Basic carrying the M14 so the stock sling placement is comfortable for me.