M5 owners, (and 18-150 ones) please chime in.

Two things that just popped in my head...

You might want to play with ALO on/off, DR+ on/off and your exp comp. ALO might be "fighting" you by pushing certain tones and not others, IE try ALO off, and +2/3 comp or ALO on (on by default) and +1/3 comp. ALO off will prevent Canon's default selective tone curve corrections to exp comp, allowing you to push the whole scene more.

Also, DR+ (highlight tone priority, off by default) both on and off are worth a shot (no pun intended) and DR+ on with +1/3 to +2/3 comp is a good idea as that should give you highlight blowout protection, with your added comp, that's actually the most logical solution, but perhaps the least purist approach.

A combination of ALO off, DR+ on, and a higher exposure comp say +2/3 is also worth a try.

Lastly if you shoot continuous, it should be noted all continuous shooting downgrades RAW data from 14-bit to 12-bit compressed. Although it's a page from the Sony/Nikon playbook, I've found it to have no perceivable impact, but perhaps with your tastes, it might. Doubt it, but if you're not using continous shooting modes, any of them, it forces RAW data and JPG outputs to render from 12-bit data instead of 14-bit. It's true impact, is by shooting 12-bit instead of 14-bit, pushing some stuff in post, in extreme circumstances, isn't as profitable. Once again, most folks aren't going to push things more then 3 stops in either direction in post, but if you do, sure, 14-bit handles better, not much, but some (as I said, extreme circumstances).