Glad it's going better now
Monkey nuts ha ha. I have no idea why they are called that in the Uk - maybe monkeys eat them in the jungle? I had a similar interesting experience when drawing up a list with an american friend to go camping - we exchanged lists - she had catsup and flashlight on her list and I didn't know what they were. I had ketchup and torch on mine and she didn't know what those were
It sounds like you've fixed the cage issues so it enables him to feel at home and have normal behaviours.
The Zombie hammie thing is kind of shock - if their nest or hoard has been messed with probably - and that can set trust back.
The next stage goes beyond taming and is bonding. When he bonds with you then it gets very special. Taming is really just them being easy to handle and pick up (and even then they will have it on their own terms sometimes) without running away or "pinging" (wriggling out of your hand and leaping 2 feet in the air).
I still often get our Syrian out in a tube or a little hide with a treat in and let him walk into that and then lift the tube/hide out (with my hands over the entrance until I can put it down in a safe place).
When he seems very tame you could even have him out on the sofa with you or on top of the bed, rather than the bathtub or playpen area - but needs constant supervision and best to have something blocking the edge so he can't leap off and run away (rolled up blanket eg) - just slows them down from escaping so you can pick him up before he disappears.
Coming out at night - this can be a bit of trial and error depending on the hamster. And ours still varies. With our last Syrian I found he was more active at certain times (and too fast when out of the cage) but more relaxed and dopey at other times (and would sit on the sofa and nap sometimes). 6 to 8pm ish he was very fast and active. 8 to 9pm ish he was more dopey and relaxed but had to be tempted out of the cage. Any time after 10pm and he was superfast (in night mode?) and almost impossible to hold for more than a couple of seconds!
Our current syrian only likes to come out about every third night - but he's older now.
Just try and leave the nest in place if you can. If it isn't soiled they will naturally keep refurbishing it - adding new bits of nesting material and sometimes chucking out some old substrate out of the door for you to take away
They constantly move substrate around and replace old bits with new bits - quite busy little housekeepers. So keep putting nesting material out if it goes down, so there is always some there.
He is absolutely adorable by the way! And you have made massive progress - because if he was 4 or 5 months when you got him he would have become set in some habits and maybe got used to ignoring humans! When you have bonded he will naturally feel safe with you - an although he might want to to just be off playing in the pen/bathtub and doing his own thing, if he is on you and hears a scaring noise, he will cling to you for safety!