Deep respect for your heroic rescue. The recovery process is going to be long but it can be fun. We are so glad you let us take this journey together with you and Stan Lee.
For the time being, he is still figuring out how the new world with you works. The new world that you have waiting for him have lots of love, toys, bath, out of cage time, seeds fruits and veggies. He haven't got a clue, so far he only understood the first thing on the list. And that is love. His current response is normal given his past upnormal circumstances. (Existing in a cage, without toy, without bath, stealing food from human plate and plucking)
From your story above, this is my translation of his bird's mind........
1) "Thank you for having me, I will show you my appreciation by cuddle up with you. I was hand fed and hence I like to stay close to you. I learned to do this when I was very young."
2) "Sounds of opened bag is my food stimuli, it means food or starvation to me. When will I get that chips from the bag again? What do I have to do?"
"I wish to eat what you eat. Can I eat with you? You are so cool. I would love to join your flock. Birds In the same flock instinctively eat together."
3) "You have been putting things called seed, fresh veggies, fruits, and pellets near me. I don't know what it is for. I have never seen it before in my life. I am not familiar with the color or the smell. Is it poisonous? I haven't seen you eat it. Nor have I seen any bird eat it. No I have not. So I don't know if it is edible."
4) "What is taking a bath? I have never been given a chance! I am not sure why I would want to do it, are you certain it is safe?"
5) "What is that new thing called toy? Is it a furniture? I don't know what to do with it. If I chew on this furniture, will you be angry?"
6) "I must figure out how to feel alive.
How to get things my way.
A Ha! I got it.
If I pluck, I get attention.
If I scream, I win."
This is a translation of bird's mind based on bird's behavioral development under unusual circumstances. Additionally, the topics that a bird's psychiatrist might suggest are as follows.....
1) Introduction of new food. As you would in a small child. (Slowly from puree to small pieces to big bites)
For example, start from eating apple sauce in front of him. Tell him it is delicious. Then feed apple sauce to his beak. After the taste and smell is liked, then in the next few days, eat chopped apple with him. Then perhaps, next week, you can eat a slice of apple in front of him.....and let him take a bite and so on with other fresh fruits and veggies.
Post in thread 'How to get my cockatiel to eat fruit'
https://www.parrotforums.com/threads/how-to-get-my-cockatiel-to-eat-fruit.91574/post-946126
2) Teaching simple commands for basic communications. For instance, I say yummy as I eat. So my Emerald knows this means food. Anytime, I say Yummy to her, she immediately know that this new item is edible.
Short, repeated words again and again always works well. Saying Good boy, praise him when he eat new food. Use praise as a stimuli. Give headscratch after training sessions.
Thread 'Tips for Bonding and Building Trust'
https://www.parrotforums.com/threads/tips-for-bonding-and-building-trust.49144/
3) as for teaching bathing in shallow dish, I suggest you get him familiarize with a hair blower noise first. Try blowing your hair from a few meters away. Move closer everyday until next to him.
I would let him take it at his own pace.
On a sunny morning.....
Let him watch you put 1cm deep water in a shallow dish. Put your hand

palm down on the dish. Talk to him, tell him it is nice and warm. Let him observe that the water is shallow. Let him see that your hand is in the water and it is safe.
Wait for him to feel safe enough to jump on your hand in the dish. If he bend down to drink from the water, he feel safe. Let him jump on the water on his own. If he does, you might need to blow him dry on a cold day.
4) As for screaming for attention, we have many useful threads. This is a short one for screams as contact call and its remedy. If your screamer doesn't stop, explain the situation in more details. So that our experienced members can better assist you
Post in thread 'GCC wont stop screaming to get my attention no matter what I do.'
https://www.parrotforums.com/thread...tention-no-matter-what-i-do.91083/post-936739
5) introducing new toys, let him see you touching it with your hands as a toy advertisement. He needs to know that it is safe, it's not going to bite.
6) for plucking ....this thread has useful detailed information......
Thread 'Plucking: A Search For Answers'
https://www.parrotforums.com/threads/plucking-a-search-for-answers.52217/
Hope this helps