Hi!
Maybe you could go a bit higher with the bounces…
I wouldn’t go lower than 0.65 int the Indirect Lighting Smoothness!!
Oh and also: I would go back to the new Volume Sample methode and not the old Sparse one!!
What is the size of the lightmap on the walls/floor?
To be honest to get that result: Postprocess!! Set the exposure to something like 1 (both min/max)! Then you can set the brightness of the scene by adjusting the brightness(intensity) of your HDRI shylight or the number of bounces also contol how bright the lighting will be!
I try to attach a 5 mins postprocess on your pic!
Good luck!!