You are so not crazy & so not the only one!

My DS is doing all of the things that you've listed. The crazy thing is that he can say sorry, and frequently does for random things that are just funny, but will not say sorry for hitting/kicking etc. he will give us a kiss & a cuddle though, so I kind of let him go on that, although as he gets older then the "sorry" will become mandatory.

I kind of don't expect there to be a quick turnaround at this age, so I focus mainly on my consistency and expectations, making sure that I'm being fair. Although I certainly struggle at times with remaining calm & rational with him, mostly cos I'm so tired at the moment.
I reckon that once you're back in your home, and things are more "normal" it will make things a little easier. And not having "back-seat parenting" would make it easier for you too. He won't turn into a monster if you use gentle methods to discipline, no matter what your family says.