Aramintai

I don't think he would want to get a Catholic looking cross. But if he wanted to, he could have taken Mariko's as a keepsake instead of dumping it in the lake.
The rest of what you've written I think adds even more fuel to the dream theory. He got a concussion and dreamt of home he left behind.
But personally I think it was just a dream. The book didn't rewrite main character's fate from his irl counterpart, so I don't think there's a room to headcanon a different one for him here.

No, the protagonist here is based on the real historical person. In the book they just loosely follow historical events. In the book at the end it was said that it was the protagonist's fate to never leave Japan, so the book didn't change this.
Go read about the real historical person on wiki:
https://en.wikipedia.org/wiki/William_Adams_(pilot)

Irl Anjin never left Japan. He later married a non-noble woman from a wealthy family, was given a house and ship building job. Ships that Tokugawa used in his war efforts. His kids were half-Japanese.
So that scene of him being old in some Western looking room with clearly full European kids must be some dream. Also, the cross he was holding was Mariko's, but he dropped it into the lake.

It only gets worse.

Yea, that muted ending and furniture of a protagonist didn't do it for me. Never once was he shown to be actually needed by Toranaga and he wasn't even funny to be his pet clown, because they communicated too seldom here. And many important scenes about the protagonist were cut to make time for a parade of side characters.
And too many times it seemed that Toranaga was just plain lucky and adapting, not megaminding everything ten steps ahead. Yea, he was a ruthless liar who surrounded himself by people he could easily manipulate, but he wasn't omniscient to predict all random things. Like, what happened to his son, or his brother betraying him, or what happened to Mariko.
And speaking of Mariko, she was more of a protagonist in this show than ML or Toranaga combined. MVP, but disappointingly way too suicidal.
My favorite character in this drama is not her though, but Yabushige - the most human and entertaining one to watch. He was squirming on the frying pan for the whole series trying to get the most profit, but failed expectedly :).

Anyway, it's still a good drama. Production quality, especially the costumes were great. Too bad they didn't show the epic battle of Sekigahara, but it wasn't in the book, so ok. I'd give it an 8. But old TV series in terms of the plot and characters were still better, imho.

I'm not talking about the rejection, but all the other dumb moments.

Do they? I've read other commenters who read it that it's a happy ending, with marriage even.

She doesn't think it will last because she'll return to the future again and then it's gonna be her dumb teenager self who doesn't even know ML and pines for SML.

Yea, at times it's just too dumb. You can say that's how teenagers behave, but FL is actually 30+, no excuses for being a walking miscommunication generator like she doesn't understand what's going on.
And ML's also rather inconsistent, sometimes he's very bold, sometimes can't even speak normally.

Why the very selective memory loss then?
Also, since she seems to be running around in the future again in the preview it doesn't look like it's just lost memories. She's changing the past. Just like with that photo appearing on ML's table earlier.

What about her younger self acting completely different when she's not in her younger body?

I'm not liking this stalker killer taxi driver sub-plot at all. Just why?

I agree with you, he's plain unlikable. Especially compared to his counterpart in the old TV series.

I already know all there is to know about the plot, so I was there mainly drooling over gorgeous costumes. Though I think they've made them too expensive in this drama, for some characters at least, with many of them having gold embroidery and very expensive textiles. I get the heir's family swimming in gold, but the rest of the samurai families and especially vassal families? I doubt that.
Still, the production quality's through the roof.

Yea, other hostages got away in the old TV series.
Not sure what's gonna happen in the new drama though, there was no other exit in that room.

They were trying to kidnap her. The context was different because she and Blackthorne were trying to help the hostages run away through another passage and she was holding the door to prevent the assassins from entering while they were escaping.
In the new version she just stood in front of the door on purpose to be blown up. I mean, what the hell 🤦‍♂️

In the TV series? She also gets blown off by the explosives at the door. But there she was holding the door from opening while others got away through another passage.
Here's the scene:
https://www.youtube.com/watch?v=RQCyAEk4yxo

I won't disagree that she's just plain suicidal in this drama. She was just looking for a spectacular way to die throughout the whole series.

In the original TV series she died by accident trying to save Blackthorne and it was more believable. And she wasn't as suicidal there either.

Her death will spark an outrage among nobles, since so far everybody pretended to play nice. But now Ishido will lose his reputation as well as substantial chunk of his supporters and will have to release all the hostages. That was the consequence of her death irl and in the book. Irl though she wasn't a puppet played by Tokugawa, she was just caught in the crossfire, so to speak. She refused to commit seppuku due to her faith and was killed by her husband's retainer when Ishida tried to take her hostage.

But here one could say everything was planned by Toranaga, including this. She leaves with his harem - it's a sign for other hostage nobles that they could demand the same. She dies - it would piss off the nobles and will make it a justifiable reason to come and "liberate" the nobles, gaining their support.

Yea, we'll see how they finish this up. But so far I'm liking the old TV series plot more.