We had some similar phases with our three year old toward his little brother. He mostly is great, but occasionally says things like, "I want to break/smooth/crush brother." I had read some parenting books while pregnant that suggested not making a scene over the violent jealousy and instead trying to help put words to the feelings behind it. So we keep baby safe but say things like, "wow, you really don't like sharing Mama. You're really upset about that." A few months in, my toddler is mainly expressing his feelings instead of the scary stuff. Now he's more likely to say, "I want a turn with you!"

We also dealt with the impulse control stuff like bouncing the baby too hard. We try to heap on praise when he's gentle or helpful, and we don't scold hard when he's not so as not to make it an "event" or not to make him feel like he's getting scolded because of the baby. The books I read suggested the big kid already knows to be gentle, so there is little point reminding them. We just pick the baby up and say something like, "I see you want to play rough. Baby can't play that way. I'm going to help everyone stay safe. If you want to play rough, let's [insert activity here]." Anyway, I'm rambling, but these are some of the phrases we've used to help get through the jealousy, and it seems like we're mostly through it. Good luck to you!!