Whimplet

Issued!!!!
Just checked status not expecting much but says issued and will be with us in 2 days...
Shocked, stunned, surprised, and happy!
Update timeline tomorrow

The London website says in FAQs
I have made an error on the DS-260, what should I do?
If you have made an error when completing the DS-260 you are required to correct the error and re-transmit it if the error concerns the Background and Security questions or passport number. Please contact us through our website as we will be required to unlock your case before you can amend the information. If the error is in the biographic details, you may notify the consular officer on the day of your interview and take no further action.
Reference- https://uk.usembassy.gov/visas/immigrant-visa-faqs/visa-processing-and-documents/?_ga=1.203886745.847207316.1438020395
I -864, part 3 is to list additional people being sponsored. US Citizens do not need sponsoring. Only your Malaysian spouse is being sponsored.

You should have marked "NO" to the question "Is this child immigrating to US with you". Like you said, the child is just moving to US not immigrating.
You should not list your children on Family member sections on Part 3 of i864 since they are not considered immigrating to US. However you count them as dependents for household size.
I think the mistake you made on DS260 is a minor one, not a major one which could easily be resolved at the time of interview, however, it doesn't hurt to call them and tell about your mistake and see what they say.

Hi Whimplet - Mollusk and I have the exactly same timeline thus far, it was also exactly two months (61 days) for us, same date of NOA1.
I think it is worth noting that while we were waiting there were two weeks where the embassy only moved forward the processing time by two days, but the most recent weekly update moved from March 3 to March 21st, so possibly a good sign for you!

Also, my NOA2 says we will receive instructions on the next steps in 5-8 weeks...

Hi Whimplet
It may not be the same for you, but it was exactly two months from NOA1 to NOA2 for me, via the London embassy.

She should bring proof of pregnancy, and the panel physician will most likely recommend a vaccine waiver based on her pregnancy.
If it was a K1 visa, she would have to get the vaccine before AOS in the US, but I guess for your visa category she might be "off the hook". I must however recommend that she does get the vaccine after giving birth, as it is an important one :-)

btw thanks A'n'L - I hadn't seen the UK forum - checking it out now