I'm using Mp3gain (for over 10 years) as well and my target level is 92 db. Your problem seems to be your sound processing. As Mastacheata wrote above - don't use default preset of SAM settings ! -. In my first SAM BC beginner years (10 years ago) I have used several presets found in the web. There was a discussion forum in german language at https://www.radioforen.de/
from where I made my first real trials with AGC settings. There are real good ones !
Additionally I can remember that someone has posted a zip file? in this forum with all agc setting trials from radioforen.de . So have a search in this forum ...
I personally have spent days to find my proper settings for my requested sound output & - in addition - with a clipping free & free of distortion sound stream.
Let me know your Radio Genre and I will have a look what is still stored on my hard discs - as I have made several AGC trials for different Genres in the past.