Maybe you should try a ride wearing something that has NO chamois padding- just so you can see if chamois padding is what is causing all your rubbing/chafing irritation problems. Maybe you need more of a smooth surface without padding that is thick/thin in various places.

I often go for 15 mile rides with no padding chamois at all and I don't have problems with having no padding. What I do is just wear some regular black stretch capri leggings and some cotton panties and (don't laugh)- a pantiliner. I found some thin extra-wide extra-long pantiliners and they totally cover over any panty crotch seams nicely and create just a very thin layer of smooth padding between me and the saddle. Works well for me, creates a seamless soft area and the edges of the liner are not near any pressure points as I ride. And they are disposable, so I don't have to keep washing my capris to death.
I don't know if this would work well for really long distances, but seems to work fine for every day type rides for me. It's cheap enough to try anyway. You could even try putting some chamois creme or coco butter on the pantiliner, though I don't put anything on it myself.