I would recommend a couple things:
1. Get the book Connection Parenting by Pam Leo
. It's easy to skim if you don't have time to sit down and read it cover to cover. It has helped us so much and it sounds like it can help you too.
2. Give him an acceptable way to express his frustration and anger -- something that does not involve throwing or hitting though. Some parents have good success with a "stomping rug." That way you're acknowledging/validating his feelings, and also allowing him to express those feelings in an acceptable and safe manner. Tell him it is NEVER acceptable to throw in anger or to hit, then give him some way that is acceptable to express those emotions. Otherwise he learns it's not acceptable to express certain
emotions and that's not good. :/ All emotions are valid. Not all manners of acting on them are acceptable, though. And that's a tough concept for toddlers to get. So giving him a healthy and safe outlet could help.
3. Try to reconnect with him as often as possible. When you can, if you have someone else who can watch the baby, take advantage of some one on one time with your toddler. As often as possible.
4. Don't emphasize the forced consequences or action *you* will take, instead emphasize the actual outcome of *his* action. For instance: "We NEVER throw in anger. Throwing hurts <the baby, Mama, etc.>! We NEVER hurt <the baby, Mama, etc.>!" If you were to focus on forced consequences ("If you do that one more time, I'll <insert whatever punishment here>") toddlers sometimes hear that as a challenge or even an encouragement, as if you said "If you do that one more time, I will do SOMETHING that will be giving you more attention." If that makes sense. So we always try to focus on the actual outcome rather than a perceived threat ("hitting hurts" instead of "hitting will get you in trouble"). Otherwise it's negative reinforcement and a child could learn to make choices out of fear, avoidance, or guilt.
5. Praising positive behavior can help but only if used in conjunction with reconnecting and establishing boundaries on acceptable and unacceptable behavior, IME. Otherwise it's just positive reinforcement, which leads to him making choices based on external validation and praise, which can cause trouble later on down the road in terms of peer pressure, etc.
Check out the book by Leo if you can. It's simply wonderful. And you might also x-post in GD if you don't find your solution here.
Good luck Mama. And sorry you're all dealing with this.
I hope it gets better soon!