Sounds like you want to paint the entire scene with a single light level solution, aka Global Illumination ? By the way auto-exposure is not GI but a means to create real world eye adaptation and not used as a means in the same manner as a brightness control and why you have a lot of bleeding going on.
What you need is a way to effect the indirect lighting levels with out effecting direct lighting levels in the same manner as a brightness control does.
Luck would have it UE4 has this ability of using an HDR map as an ambient cube map available in the post processing volume.
https://.com/watch?v=VYNFdZhcEwk
As you see you can then increase or decrease the ambient fill with out blowing out the direct lighting. A bit of a cheat but somethings one needs a bit of help turning the dial to 11. 