Poop Question: 4 Weeks

I have of course witnessed this question and similar here before, and I apologize. But I have yet to find the answers I need for my specific situation and hoped it would be best to create an account and ask myself.

My husband and I live on a farm with many animals, cats included. One of our females apparently had kittens recently, but we only discovered one survivor in our barn. She had abandoned him in a bag of cat food, leaving us to assume she was trying to teach him to eat on his own. We aren’t exactly sure his age. She was completely done with him, obviously. But he is still very small. My husband brought him back to the house and we took responsibility for his care.
I would assume he is four weeks at least, give or take. He has all his teeth, his ears are fully open, and he is a very adventurous and happy little guy. After one night of spoon feeding soft kitten food (smashed up with warm water), he took to the kitten food on his own and eats like a little piggy. No problems there what so ever.

He still won’t drink water by himself. But I have had no issue giving him water by spoon at every meal. He just seems uninterested in it, but he drinks it from the spoon just fine.
He has been in our home for about 3 days now, and has gone wee just fine about 3 times. But still no poop!

He is s very vocal kitten, but does not seem to be in any pain. He is mostly just bratty, crying when he wants out of his box or to be held. He loves to snuggle, and has recently discovered the joys of string. He sleeps plenty. His belly isn’t hard and doesn’t seem bloated. He doesn’t seem dehydrated or sickly in any way. Actually, he seems completely healthy.

He runs around, climbs, plays, cuddles, purrs. He is honestly one of the sweetest and smartest little kittens ever. We have taken to calling him “Jelly Bean”.

I’ve tried the warm rag/cotton ball to stimulate him with no luck. I tried a warm Q tip slightly in the bum. All it did was make him mad lol.
I’ve begun to worry, even though he seems healthy and happy.

I feed him a little bit of the mushy kitten food about three times a day, sometimes four if he seems focal from hunger. I give him about 4 or 5 small table spoons of water after each meal. I snuggle him and play with him constantly, and always make sure he gets plenty of sleep.

Am I doing anything wrong? When should I worry or take him to the vet? (Of course I’m taking him to see a vet for a check up anyway. But I am also currently in labor, five days away from my due date, and don’t plan to take him unless I need to until after my son is born.)

Any advice will be greatly appreciated, and thank you all so much.