Everything that has been said seconded.
I'll add this:
- Do yourself a favour and tweak at least 2-3 of the most common sounds you typically use at gig/rehearsal level, ideally with some friendly bandmates allowing you to do that while jamming. Once you find something you're happy with, save it for future reference (you could then compare any new homebrewn creations to those).
- In case you want an easier tweaking experience, insert a looper as the very first block (I know, there's a shortage of blocks with the Stomp, but this is just for the initial setup, you could replace the looper with, say, a drive block later on). That will allow you to tweak while the looper is playing for you. It will even allow you to, say, move the Headrush into different positions while listening. Fwiw, regarding the latter, I always found a little utility case (that I carry with me all the time) below my FRFR to be sufficient in terms of adressing whatever low frequency "coupling".
- For a short term remedy, you might want to check the global EQ. To at least kind of defeat the mentioned Fletcher Munson effect, a rather broad mid boost (atm I have mine set to 750Hz with a Q of 1.2, but you might need to experiment) could do a nice job already. Make sure to check at least the low cut, too. You might be able to get through a rehearsal easier that way, then, back home, you could try to move those EQ settings into the patch somehow, so the global EQ is freed up again (which always is a good thing).
- You might want to use some mid-heavy IRs. No real recommendation from my side as I'm using 1-2 pretty heavily customized IRs that I grabbed myself (I could post these, if you wanted), but I remember one of the York Audio IRs (from the cheap $1 teaser pack) to be pretty decent, but I wouldn't bet on it. In case you're using the internal cabs, try to find one that's more on the "warmer" side of things (which usually indicates more mids), possibly use one of the ribbon mics or just the good old SM57 with distance and early reflections turned all the way down (fwiw, unless you're in a recording situation, I would always turn early reflections all the way down).
- Prepare a bunch of patches like that, each featuring somewhat different overall frequency ranges. You might not have enough time to fiddle around during your next band jam.
- Try to borrow another monitor for a rehearsal. The HR 108 possibly isn't the greatest thing on earth. Even the difference to the sort of similar Alto TS310 (which I'm using) is very, very noticeable, especially the low range sounds a lot more balanced (I'm pretty sure they tried to get more "ooomph" out of that 8" thing via DSP processing, which usually doesn't work all that well). I wanted to get the Alto TS 308 (almost identical to the HR) as a smaller alternative, so I compared them side by side - it's been quite an eye opener. You might as well find a Yamaha DBR10 or DXR10 to try out, they're very common (fwiw, I also compared these to the Alto TS310 and they weren't any better for my purposes).
- As a last thing: Keep it civil with any kinds of room FX when trying out sounds. IMO, a great sound should work well without any (unless you're exclusively into ambient things), so you might only want to look at them as the final icing on the cake, not treating them as a necessity. Fwiw, this is what helped me a lot ages ago already. Anything roomy won't just repeat whats wrong in the first place, it'll also mush it up, making it a lot harder to pinpoint the real issues.