If the Thai embassy in the country where you are applying from (where you physically are) only accept card payment, then get a friend/college/family to pay with a card and give them cash. It's not a fortune.
there is no chance of visa type, he is already on yearly extension. He apply for the 60 day visit family extension, and then again a yearly extension. It is all based on the same reason (marriage to a thai) and is perfectly doable. He is not applying for a new visa when doing this.
he is not asking about monthly transfer, but using an affidavit from his embassy. And as he is from Italy, if they ever did it, they probably still are. Danish Embassy still doing them. Only a few stopped. If you have that, you don't need either monthly transfers or a lump sum.
my experience with them was very positive. But yes, they will look for reasons why the applicant will travel back to Thailand. Being your girlfriend and you covering the trip doesn't cut any ice. They want to see her connections to Thailand. Reasons why she won't just go there and try to stay there. Job. Kids in school. Owning a house. Etc. If married it's much easier though.
VFS global offers several add-on services. For example documentation and filling out forms. Go look on the website. You are going to apply through there anyway.