Yeah......I love 748 but never use it below about 45⁰ and every time I buy it I break down and get an eight-pounder because all my loads are off considerably. I've said it for years, Hodgdon gets a train car load of ball powder and tests it and depending on which ballpark it tests near it goes in bottles marked ww748, H335, or BLC-2, and the next lot will be different.
IMR 3031 is a truly impressive powder with cast bullets in .30-caliber cases on the small side of medium capacity. Gentle launch yet a sustained pressure curve and very easy to light-off and consistent. With the long jump you have, why not switch to a cup point pin in the MP hunter mould and push them up to at least 2200 fps? The nose taper of that mould is much better suited to the jump than the two-diameter 311041 which has little to keep the nose steered straight.
As for your first-shot flyers, I reiterate that with the MP bullet you have a lube that isn't making your system happy. It is fairly predictable though, so the easiest fix is aim a little lower for the first shot.