Wicking is very important. I'd suggest trying rayon if you haven't, it's rather forgiving as a wick material compared to cotton, I have found. Less leaking if used correctly (rather tight in the coil, thinning and cutting wicks etc.) and the wick lasts longer, always a nice thing.
I have found (most often for me) that popping and spitback are caused by wicking issues, or if trying to run a too low resistance coil with low wattage. You probably want to focus on smother wicking, and (counterintuitively enough) sometimes less wick is MORE. Tightness in the wick is what keeps the pressure okay, but if there is too much wick in the tails it can actually clog and work LESS efficiently than tails that have been thinned out a bit (I use the non-ceramic tweezers that come with my coilmaster kit, it works well) and can thus more efficiently wick juice.
If wicking changes don't help, you can certainly add DW. I was using max VG for a while (PG sensitive) and found adding 10% DW to be a help. Before amending ALL your mixes though, you could try adding a little bit of DW to your tank directly, to see how it improves things. You don't want to add DW to all your mixes and then find you don't like it and/or it doesn't help. I will say that DW improved my vape quite a bit, but my PG content is flavors only, so under 10%.
Best of luck, I hope things get better. Watching some YouTube videos on wicking your device may help you (if you haven't already).
Hope you get it sorted out.
Anna