Defiant toddler

My son is 20 months old, so he’ll be 2 January. Ever since he was about a year old he started throwing his toys. I, being a FTM, was concerned and googled it & read that it’s normal and it’s just how kids learn cause and effect, but it persisted and he started throwing toys at others, and I made a post about it and someone suggested I was being to soft, by just telling him no, and I needed to take action & take toys away. And I agreed with them, I still do.

But it was ineffective because since my son is still in a crib, he doesn’t have access to his toys is his bedroom, they’re all downstairs in the living room and he has a treasure chest full of large plastic (painful) toys like trucks and cars ya know typical boy toys. His behavior has gotten worse and worse over time. I don’t know what the hell in doing wrong. His father and I are not aggressive towards him at all ever, but he slaps and throws toys and screams and throws the worst tantrums.

And lastly - so my son has a few sitters that he goes too during the week so my fiancé and I can work - and they all have pets & my son has always been really sweet to animals. So when a friend of mine needed to rehome her cat, my fiancé gave me the okay to take her in - but my son chases her around with toys and hits her and she’s petrified of him & hides upstairs. She won’t come down until my son is sleeping. And obviously while he has some comprehension, I don’t know how to articulate to him that if he were gentle and less rambunctious around her, she wouldn’t run away from him but he’s not even 2 yet so idk what to do - I feel like taking the cat in was a big mistake but I’m hoping in time his excitement will wear off and he won’t go nuts when he sees her & they’ll be able to coexist together.

Anyway. I’ve resorted to putting his chest of toys in his room - keeping only soft toys down stairs in the event he does throw them (which I know he will) at least they won’t hurt anyone or anything. For the longest time we had to block off an entire section of our livingroom because my brother let my son get into our dvd collection not realizing he was creating a habit and that area of the house became a catch all and it was an absolute eye sore, and I was sick of having our treadmill blocked off as I’m only 30 lbs away from my goal weight & I didn’t want to have any more excuses for myself not to put the damn thing to use so I cleaned that area up and took the gates down but I’ve since had to move all the DVDs on the lower shelves to the upper shelves to keep my son out of them because no matter how many damn times I’d tell him no and take DVDs from him and put them back, he continued to pull them all out.

I feel like I have such a defiant, naughty child. And idk how that happened because I have never thrown my sons toys, I have never hit him, idk where this behavior is coming from or how to remedy it. Ive read all over the internet to “gently grab his hands and tell him no that hurts or don’t hit mommy be gentle blah blah blah” and personally I think it’s a load of shit because it doesn’t work. I can grab him hands and try and tell him no be nice but he’ll just scream and throw a tantrum so he can’t even hear me and it just makes it worse. And I have other mom friends that wanna get our kids together for play dates but I’m hesitant because I don’t want my son to hit one of their kids and feel even more ashamed and embarrassed of his behavior than I already do.

What am I doing wrong!? Please help!!!!! 🥺😭

Edit - I just wanted to note that by a few sitters, I mean he goes to a sitter for 2 hours and then his grandmother has him for the rest of the night until my fiancé and I get out of work, and on fridays his aunt picks him up from the sitters house. So I wonder if it’s because maybe they aren’t consistent in their disciplinary actions. I know his sitter obviously doesn’t hit him. And he’s usually well behaved with her. He has like half an hour of play time and then he has lunch and naps until he gets picked up by grandma or his aunt. And I know my SIL doesn’t hit him. He’s usually well behaved for her too. But my MIL has mentioned on a few occasions when he slaps her, she slaps him back. And I’m not okay with that. I understand that it’s frustrating and it’s hard not to get pissed and lose your patience after he’s hit you repeatedly after you’ve told him no, but I think her hitting him back is confusing him. I don’t wanna have to say something to her because her and I have butt heads in the past due to her undermining me. So I asked my fiancé to say something, but he doesn’t think she’s done anything wrong & thinks that hitting him back will teach him not to hit. But obviously not....