Fiance to Spouse visa questions

[Incy]

Hi all,

I have been searching and can't really find much to help me with some questions I have.
The solicitor I have been using seems to have gone AWOL at the moment as well, so can't ask them either.

My partner got his fiance visa granted on 21/12/18 and came to the UK on 29/12/18.
Wedding is booked for early March and we are starting to organise things to also have documents that show he is living with me.

A question I am struggling to find an answer for is;

When we are married he wants to take my name (it is a same sex marriage), but his passport will obviously be in his 'old' name while we are applying. We know that he doesn't have to change his passport when applying for the Flr(m), but his passport expires Feb 2021 so will be expired before we can reapply for the spouse extension, does anyone have any experience of this?
He is from Malaysia, no sure if that will make any difference, just wondering if the process is different dependant on his nationality.

There will probably be more questions as I think of them....