Great question actually! What we hear most often is a perceived acoustical pressure and the mass or body of the sound moving in a larger space. Been there just like you man - using in ears trying to have my main sound fed through FOH and in ears sounds way different. That's only because we perceive sounds in different environments and different distance differently.
Have you ever noticed that you have a slightly different sound in your rehearsal room and on stage? I did. Each time I'd fire up the amp on stage I start lowering presence/treble and sometimes mid control and that's just because sound in an open space behaves differently than in a smaller one.
Also hearing your sound whether that's a real cab or a torpedo is a way different experience from a distance and then straight into your ear canal.
What helps here is if you used a bit of a room reverb with some advanced tone control that you can set to a lower tone setting, rounding it up. This will warm it up and behave in a way that your ear and brain is used to and what you like.