I say all of this with love and knowing it doesnt give you the quick fix answer you want...
He is a difficult age. In my experience from my three children, age 3 was hard! And also each transition to a new sibling... I read something that said they are literally grieving the life and relationships they had before baby came. He will be absolutely fine in time but he deserves to have the recognition of what hes going through, regardless if that seems to be his "problem".
I know it is really tough, but Id encourage you to work on your mindset. If youre viewing it through the lens of him "ruining your life", your brain will already be looking for the evidence to support this, he will be picking up on your attitude towards him and is probably feeding into it etc. This is so hard to do especially postpartum and exhausted taking care of a new baby, I totally get it. But you kind of have to fake it til you make it... try hard to reframe it to he is a good kid having a hard time, try and focus on the tiny moments of joy even if it is as small as holding his hand as he walks up the stairs! Im talking tiny!
My practical suggestions are to not stress yourself out over "1 to 1" time, small moments like 15 mins uninterrupted play that he gets to lead, cuddles and stories etc. I always find getting out the house so much better for everyone, even if it is the last thing I feel like doing or it feels overwhelming. Parks, walks, scooter ride, softplay, farm trips etc. Baby in carrier, couple hours outside and then you can chill out a bit at home. Try and have easy activities at home - puzzles, stickers, playdoh, building stuff etc. Play with him for a few mins and then hopefully you can sneak off and he will play a little alone.
Have low expectations - everybody fed and alive is good enough. Make packed lunches night before or when you have a minute, then you dont need to stress in the moment when everyone is hungry. Dont feel bad for screen time or snacks, it is a season!
Also to add, sleep at this age has always been rough for us!! Be consistent and calm as much as you can, tap in support from partner, or if you have to do things like a car bedtime do it! I resorted to that a lot when heavily pregnant with my third and two toddlers at home!
I promise you it gets so much better, youre in the trenches and the fog will lift Xxx