I Don’t think so for the headphone output, cause i use some IEM sometimes (20ohm) And It Works too
(i have to push higher the knob with the 250ohm headphone...normal)
Did you try on the global settings to put on « guitar in pad » (for the distorsion problem)?
I play Bass too on my Helix... a question that may seem stupid but if it's an active bass, have you check the batteries. It can explain the distorsion and low volume