We're struggling with our 4 yr old and nearly 3 year old boys, however, we don't get the backchat...yet.
DS1 didn't even want a kiss goodnight from me the other night As I type this, he's doing my head in, he won't leave his younger brother alone...

I second what some of the others have suggested and try to schedule some fun activities for you both.
I also find chucking them into a warm bath in the afternoon when feral hour hits, can work wonders and just sitting quietly, reading some books can settle them a bit.
Our boys have the selective hearing too, but I'm getting the eldest one to do a few things while I'm feeding DD, by playing on the 'big helper' thing and giving him special jobs.

I can't remember where I read/heard it lately, but instead of asking them to put their shoes on before we go out/go to the toilet or take their shoes off before sitting on the couch, I ask them 'what do we need to do before we head out?' and get them to answer the shoes part and make a big deal out of it. What are our rules about sitting on the couch? (shoes off). For some reason, this works better than just asking them to do something.

I hope things improve for you soon. I really don't think you're a 'poo head'! Hang in there and ...how long until she starts school?