Do you think Ray on the toilet on the porch represents

Could be. It grossed me out as much as the naked fat chicks.

It represents how *beep* is done in Texas.

Because of the abortion, life turned to sh!t!

JK

I just saw it as Ray being a trashy person who thinks he is clever. Also as a way for him to attempt to intimidate people through a false sense of vulnerability. He's sitting completely naked on a toilet in the outside of the middle of nowhere, each something that should represent a form of vulnerability, and openly mocks each one. The look he gives Andes right before he wipes has that distinct "Two can play this game" vibe to it.

There's a difference between a differing opinion and a forced one.

Perhaps it was related to Susan.
I think it may be the new husband... on one hand. He blatantly is taking a dump - maybe like the husband caring little for the relationship and not hiding it. Also, there's the talk between the two men at the end when Ray confesses to raping Tony's wife and killing his daughter, and mocking Tony for doing nothing about it. Sound like someone we know?

Also, he may symbolize life, or a certain type or aspect of life when he says he basically is whatever someone calls him. He proves them right.
On the other hand, you can look at the new husband from a lot of angles - including a cheater - which Ray mentions, likely not by coincidence, as an example of whatever someone says he is. He is a cheater. Maybe emotionally he is a rapist and a killer from the perspective of Edward's and Susan's relationship.

Maybe the book is the gesture that is meant to "kill" the new husband.
However, Edward is likely dead inside, perhaps with bitterness from the past similar to how the detective (who symbolizes his current self) is being consumed with cancer.
It's Tony who kills Ray and also dies... Tony is Edward's past self. He uses him to get revenge against the new husband.

The detective doesn't show up for that, but he gives Tony the ammunition to do the job (as Edward did for his past self by writing the book). Also, the detective kills the accomplice before he can get away. This is Susan. She was a participant in the whole mess, but not the mastermind - just like Ray's accomplice (pardon me for not naming names). The detective kills him - and present-day Edward gets revenge on Susan and perhaps had to - maybe for a chance to move on in life. He had to let her go, and in a sense killed her in his mind... "her" being the person Susan became after helping to kill the person Edward loved as well as literally killing the child he was to have with that woman.

When Tony breaks down, it could be that the "I should've tried to stop it"...