I could have written all of this about Leo. He's 15 months too and is a stroppy nightmare at times. He's also incredibly cheeky and mischievious and very lovely at times too.
I have adopted a zero tolerance approach to hitting. Telling him no didn't work. Neither did saying ouch and showing him how sad he made me or whoever was hit so now if he does it he goes straight into his buggy for a few minutes. While he doesn't understand time out yet he knows full well now what happens when he hits and has, for the most part, stopped it.
Yesterday we had a bit of a showdown about him helping to tidy up his bricks, he went through the full range of tantrum, I'm wounded, distracing me by pointing out the window, asking for cuddles, stomping, raging, tickling me before he realised none of it was working and helped me put them away. All I did was return him to the bricks whatever he was doing and cheerfully said we need to put them away now. I had to say it at least a hundred times but it worked. I ignored the tantrums and bad behaviour and when he was trying to distract me I just kept saying no, we will cuddle/read/look out the window etc later once we have put the bricks away.
I find with Leo repetition is the best. He has to sit down to drink his night time milk so rather than keep telling him no I just put him back to where he should be and tell him that we must sit down when we are drinking. I keep doing it again and again and yesterday he did. I ignore him completely when he tantrums about being put back and just keep talking in a cheerful calm voice after he's stopped.
He does understand no and stop but he doesn't always listen but I have found the less I use them the more effective they are. I try to use distraction and encouragement to stop the behaviour before it's started and I keep reminding myself (thanks to The Bag) not to sweat the small stuff. If he's about to touch something that he shouldn't I just move him now and try to distract him with something else. I keep the sanctions and sterness for the anti social and dangerous behaviour.
It's the end of the world as we know it and I feel fine!