This is why you need a lawyer
UK company but based abroad - which law takes precedence in conflict - most UK co would say UK law but we don't know and sounds like you dont either
Them not being compliant to contracts/racism and other issues is a bit of a red herring at this point - but useful when negotiating settlement in stage two
Just because they have scheduled a meeting for Monday doesn't mean you have to go - its not enough notice for one, especially if they are expecting you to get legal advice. I would write an email to the effect you will not be attending as you have booked legal advice but not yet been able to receive it because of the insufficient/unreasonable notice for the meeting.
First thing Monday set up legal advice asap and ask for free dates to attend a work meeting from the lawyer, even if online over zoom etc. Then offer this as a date for a meeting as an alternative in your email to HR. Do not be kowtowed into a meeting prior to that or even get caught in a meeting with the relevant people - just hang up if that happens.
FOr lawyer advice you will need a copy of hubby's contract and anything received from HR
Yes to putting in a freedom of info request - but timelines are not immediate on that - but again don't be kowtowed into a meeting before that available.
It is normal that the employee goes off with stress in these circumstances - it is not a good environment to be in even if remote - I suspect he will be cut out of all comms except via HR. Get the FOI requests in using lawyers wording, follow his advice, be very objective in dealing with it = try not to take personally and get emotional - leave that till all over.
Don't just push for notice and leave there should be an additional sum, particularly if they are doing this to avoid redundancy etc. That's the point where you start bringing in the other issues not dealt with by HR and if pushed start talking about how that would look in the papers. Holidays and notice period are payable by law they can't withhold it for an NDA, any settlement it is more usual to have an NDA.
Be ready they will utilise every malicious act they can to corner you. I have guided friends through at least 3 of these and all won with significant settlements - 2 went to tribunal and got strips ripped off them by the judge for their actions.
You have to show you know the law, have the support of good lawyers and are prepared to stand up for yourselves. It takes nerves of steel to be honest.