Lmao...Actually the best advice is to ignore him. Don't let him see you get frustrated. He's at the point where his brain is in more control than he is. It's something that allll toddlers go through.
Maybe you oculd ask him if *he* wants to wipe his butt. I'm sure he'll feel more of the independance he's trying to have.
Ask him to wash his hands after he's wiped his butt, and so on.
This is actually something that they cannot help. They're not doing it on purpose. They feed off of the emotion that you give him when he reacts in this manner. Ya know?
If none of this works, just say "fine, i'm not the one with poopie in my butt" and walk away. I bet, he'll come to you and sya poopie as in he want's you to change it.
I saw this on "surviving motherhood" on the tlc channel. It worked wonders for the mother!!
As for the temper tanrtums, you should use short direct corrections. Like come here now! Or stop it now! Nothing like "hey, I don't want you to do that because you'll break it hunny". They don't respond as well as we would wish they did.
With the tantrums, let him go. Make sure he's in no physical harm and let him see that him doing this, has no effect on you at all. He'll realise that that doesn't work anymore. So he'll maybe try to converse with you instead of spazzing out!!
I hope this helps a little. All the little man wants is independence probably. With the new baby coming, he'll need to start practicing!!!
Sarah