IMR3031 has been the old standard for jacketed bullets (150 & 170gr) in the 30-30 for years.
Check the data again and make sure the loads data isn't for 150 Jacketed bullets,, and not inclusive of cast lead bullets.
LEE often simplified data and listed jacketed & cast bullets of the same weight under the same powder charge loads. Don't know if they still do that.
Plated lead is still a lead bullet, it's not a real jacketed bullet.

IMR only lists a jacketed bullet load w/ 3031 that I could find.

H4895 works very nicely in the 30-30 w/ 150 cast. I use it in the 30 Remington also.

I think you're just pushing the lead bullets too fast and the powder doesn't lend itself well to a deduction to the velocitys you want to get down to w/lead bullets.

The 30-30 is a very accurate lead bullet cartridge at mid-range velocitys and below.

added:
If you just want a light comfortable plinking load w/the cast bullet,,Red Dot powder loads in 30-30 are very nice.
Anywhere betw 6.0 to 7.0 gr RedDot under a 150 to 170 gr bullet.
The only one I ever got to check the vel on was some 165gr GC w/ 6.5gr RedDot. They went out at 1050fps IIRC (24" rifle bbl).
Plenty of powders in that catagory (shotgun/pistol) to use for light loads. Very accurate too.