Totally get that with the airlock gunk, had the same sticky mess once. A tight weave cotton cloth, like a clean tea towel, is the real move for kimchi. It lets it breathe and bubble over without making a lid pop off. Just make sure the cloth is big enough to tie down tight so nothing sneaks in.
Airlocks always felt like overkill for kimchi, like using a race car to get groceries. My last batch with an airlock got gunked up and actually stalled, which never happens with a simple cloth napkin over the jar. It lets the gas escape without letting in fruit flies, and I haven't seen a spot of mold since switching. The cloth just works better for the way kimchi bubbles up.