Reading the post I think I am pretty comfortable with recoil I shoot a 338 win mag now in a old red but tang safety Rugerr M77 have never had an issue with recoil in it.
I think there is a substantial difference in recoil between a 9.5#-10# .338WM and a 7# .300WM but that's just me. Most of the guys who were shooting light .300Wby Mag rifles with me had breaks and they were tolerable. I absolutely hate breaks. A can will do you a world of good but I wouldn't hang a can on a Douglas #2 or #3 barrel and I honestly don't like to thread barrels that slim either even for a break. In a light gun I think the answer is less recoil. I shoot thousands of rounds a year through work rifles, match rifles, and smokeless muzzleloaders so I may have evolved a recoil aversion.
Leupold makes decent rifle sights but all of mine have become backups to better sights already mentioned.
You might look at different shooting venues around you and see what sort of matches they offer. One of the better events I've done to let you know how you feel about toting your stuff through the mountains is the Mammoth Sniper Challenge at Rockcastle Shooting Center in KY. I carried a 46# pack and and 18# rifle for that event and wished I had brought a lighter gun at times until it came time to shoot it. I carried it for roughly a marathon there over three days. I am shooting a Run and Gun 5k there in March and will carry a lighter gun but it won't be a 7# rifle either having shot long range in the mountains after long fast climbs. Run and guns exist all over so find one and tote either a light gun (your 257IMP) you have or a heavy gun (your 338WM; most matches allow bullets under 200gn and under 3000fps from 30 cal or under) you have and see what you think the realistic happy medium is for you to move with and shoot well under physical stress.
I hope this build pans out for you but I think you either need a smaller cartridge in that gun or a little heavier gun in your cartridge choice. It's a right tool for the job question. I don't drive rail road spikes with a small ball-peen hammer. I don't generally choose to shoot long range with bantam rifles chambered for big rounds and small optics although it can be done.
