Top of the line Shure doesn't probably have enough output for your receiver's phonostage. OR contrary your phonostage is designed for MC cartridge while you have MM cartridge.
Budget Solution to your first problem:
Since you've already paid big bucks and don't want to loose them you should acquire an outboard phonostage with higher gain. Sumiko phonobox or Nad PP1 comes onto mind and will straighten your problem.
Solution to the second:
Replace an input resistor(physically remove and place different load with soldering iron) or if adjustable adjust load resistance to 47kOhms. Inspect inside and outside the box if such could be adjusted via switch.
Budget Solution to your first problem:
Since you've already paid big bucks and don't want to loose them you should acquire an outboard phonostage with higher gain. Sumiko phonobox or Nad PP1 comes onto mind and will straighten your problem.
Solution to the second:
Replace an input resistor(physically remove and place different load with soldering iron) or if adjustable adjust load resistance to 47kOhms. Inspect inside and outside the box if such could be adjusted via switch.