Let me say up front that I'm not a child psychologist or an expert at all. I'm speaking from experience with the multiple difficulties we face.
I am the stepmother of an 11-year-old daughter who was diagnosed with ADHD at age 6, and also has a psychological condition called Reactive Attachment Disorder (RAD). In short, she has the very short attention span of any other ADHD child, but she has the added difficulty of not being able to connect emotionally to ANYONE, including her own family - she just doesn't care, as her counselors told us, so she doesn't learn from her mistakes and she will almost always do exactly what she wants, no matter if it's right or wrong, without thinking of the consequences or caring what they are.
All that said, we began seeing increasing difficulties about a year ago, in school and at home, including hygiene issues that seemed more like 4-year-old behavior than 10. She is taking Ritalin LA, which she only has to take in the morning, so the first thing the pediatrician did was increase the dosage by 5mg. This helped her with better concentration at school. It seems that if you have a child with ADHD that does not grow out of it, the dosage has to be increased as they grow - it's relative to body weight. When the Ritalin LA wears off, around 3:30pm for her, the pediatrician gave us Ritalin 5mg, the short-term version, in case she has some kind of homework or book report that takes her beyond the 3:30 transition to "critical mass" as we laughingly call it.
Our situation is different with the Attachment Disorder added to the list, but we have been learning a lot about discipline and consequences for a child that seems to start over every day and doesn't retain anything or learn from her mistakes - she constantly repeats the same behaviors, makes the same mistakes, receives the same consequences, but then it all starts over the very next day.
We were taught by her counselors and through a book they recommended especially for RAD that getting angry is normal, but it may be what they want to see. It's a reaction...it's attention...negative though it may be, it puts the focus on the child. They also told us that by age 3 or 4, a child is very aware of what they've done wrong, so long lectures (which we became pros at doing) are simply a waste of your time and energy. They recommend a "hit and run" method for punishment. For example, if your son leaves the shower curtain open, when you go into the bathroom and find it, call him in if he's not in there already and do something like give him 10 push-ups. Tell him he should know why he got in trouble and walk away. That's it...it's done, enough has been said, and it's over. Then, until he can prove that he will close the curtain, as you have repeatedly asked him to do, he can only take baths.
As for the wiping issue, maybe you can try something like making him wash out his own underwear in the sink when it's dirty. When he stops, they go into the laundry with the other things, as usual.
Essentially, we were taught that if the consequence is in direct relation to the "crime", it has a bigger impact.
Again, this is just my humble advice from a fellow frustrated Mom who hopes it will get better for you.