I'm getting seriously stressed with this and need some advice
My ds is almost 3. Was always praised absolutely everywhere by everyone for being the sweetest well mannered gorgeous little boy.
Ds2 arrived 6months ago and all was well for 2 months then started to deteriorate.
I just don't get it. We give ds1 so much of our time, at least a few hrs a weekend one of us will take him out on his own and do something, or get my mum to have ds2 while we all go out as a family of 3 like old times.
He talks about the baby to everyone and calls him his best friend. But he's so damn rough with him too, and not even secretly. He will be sat making him laugh (baby finds him hilarious) and they'll be having lots of giggles together, then ds1 will just shove him over, or throw something at him. When baby cries he says "haha".
That's the bit that I find the most infuriating 
Tonight i was drying the baby on my bed after both boys being in the bath and ds1 came and whipped the covers off the bed whole ds2 was lying on top of them, resulting in baby almost crashing to the floor. I caught him at the last minute.
I feel like I'm getting into a spiral of constantly having the "be a good boy not a naughty boy" chat.
I tell him off and he grins the whole way through, I send him to his room and he plays with his toys. I tried the naughty step but it just seemed to detract from the reason he was there in the first place (as then it was a battle of wills over him actually staying on the step so he forgot the reason he was there in the end)
I've tried the whole gentle parenting explaining how he must make his brother feel
I've tried ignoring him totally when he's mean and giving all the attention to the baby -to be honest this does work the best but then I feel like a shit parent for feeling like "you just kicked your brother intentionally but I'm not going to tell you off".
I hate feeling like my lovely boy has disappeared forever.
Anyone got any words of wisdom / advice? Is this normal and will he outgrow it?
My brother has kids who detest each other, all they do is scream and fight and I am just terrified that this will be my boys too. I'm trying so hard :-(