Dusty Rivers, gotta cheap GPS? Borrow one. With SA switched off they are accurate to about 30 feet or less, usually 18 feet, where I live. Walk it and mark it various spots on the field. Plant a survey stake and take notes. You will be very close
I made a couple of different length shooting sticks from Varmit Al's site for situations like this. Once you get the feel for them they are rock steady. Check it out.
http://www.varmintal.com/ashot.htm. Or, build yourself a rest on your porch.
You will be shooting up hill, but if the rise is only 30 feet, probably would have little effect on trajectory and POA. Acute angle up or down, you will shoot slightly below the flat land POA.
For long range, steady rest, learn to dope the wind and PRACTICE. Set up a target at that range and try it out. At the end of the day, I will only be able to extend my range to 300 yds. Wish I had a field like that....hog heaven, no pun intended. You got Hogs????
Can't help you out on the load, but others will chime in. Don't own one.
I will check out the ballistics and follow this thread.
Ken