Of course it can be cheaper. UK passport applications need to submitted in person and collected in person. So it all depends where someone lives, nothing to do with laziness.
You might look at using a Headunit Emulator app on any Android tablet and continue to use your phone for data and GPS purposes. Turns the tablet into an full function Android Auto display (apparently).
The issue is not what "they" will accept it is whether or not your bank card, from whatever country, will work for an offline payment in the UK. The question needs to be directed to the bank, HMPO don't care.
I was hoping the reason for all this nonsense was a mental illness, it would be terrible for a sane person to behave like this (unless being paid to do so which is possible)
I don't know where you are reading but on the main GOV website (https://www.passport.service.gov.uk/overseas/information/thailand/renew/adult) nothing has changed. You still fill in the form and VFS then send it with the application to the UK.
The question with the Thai debit card is whether your bank will accept an overseas "cardholder not present" transaction. HMPO will not have any problem if that is the case.
It had to be paid by card. Payment is taken in the UK. It doesn't have to be your card. Or your daughter could send you your new card details although you will likely have to activate it somehow.
Well the embassy would have already issued that years ago. But in any event getting a new document proving you're not married is not going to help much with getting a marriage extension.
https://www.keyvisathailand.com/services/renewing-uk-passport-thailand/ is another possibility. Pattaya based but that is not an issue as you only have to send your documents to them by EMS.
If TG's system is in any way "clever" it won't allow the booking as the passport expires before the flight. Of course the only way to find out is to try it.