So I'm currently in the 1.8.9 and wonder whether you can turn off the damage with a gamerule without going into creative
Which exactly are harming?
Just give yourself resistance
Actually you can only deactivate false damage, fire damage and PVP damage. You could also set the game to Peaceful then you wouldn't get any damage if you switched off false damage, fire damage and PVP damage with gamerole
Also turn off air bars