Well I set both my sci and accolc to the lowest even the accolc
, every phone I get.
I even work on the fringes of service with a pretty weak radio and still don't have any problem with getting calls, even when I break up for people listening, my phone still rings.
It sounds like you've done most everything and you are getting 80-90db which is decent.
If you've done all of this and tried different radios, maybe you just have a bad/weak radio hardware, there has to be random bad or weaker ones, if you have TEP just do a swap.
Some roms have a Setting enabled to switch between 1X and Evdo or Hybrid....the setting is under Start/settings/phone/service/mode of operation/get settings
If that is not there it can be enabled by doing a reg edit
Go to HKLM/software/oem/phonesetting there is a Key, change HiddenModeOperationPage value to 0
The setting should now be visible, don't need to softreset even.