The only thing you'll receive is your visa as a pdf document which will be sent via email. You can also get it by logging back into the e-visa system and printing it from there.
that's not even counting if the previous one was a conversion+visa done on an impossible timeline or they got the extension from a far-flung province. Both of which would make it impossible to get off this year even if you had your own money all year.
if he used an agent last year, he needs to be able to show he met the financial requirements of last year's extension. That means 800,000 in the account for 3 months after last year's extension and never letting the account drop below 400,000 the rest of the year. PLUS the monthly transfers to switch to that method this year.
the best advice is to go to immigration and ask for their current list of requirements for marriage extension. Unfortunately even this doesn't guarantee success as there are often items that are not on the list.
you already have the visa, so you won't be getting a new visa. For retirement extensions, those are usually processed same day. Some offices like Pattaya require you to come back the next day to pick up your passport.
You didn't get your visa from immigration if you have a non-OA visa. You got it from a Thai embassy.
A certificate of residence is issued by immigration.
Whether or not you need a lease will be up to each individual bank branch and what their policy is for new bank accounts. The manager at each branch gets to set the requirements. If you don't like the requirements at the branch you go to, leave and go to another one.
The law that created the DTV says you can convert to other visa types while inside of Thailand. Whether you're actually able to do so will be up to your immigration office at that time.
First of all, no one can help you if you don't say WHERE in Thailand you're talking about.
Second, very few agents want anything to do with a marriage visa/extension. These have to go to the regional office for approval, so they can't skip the requirements like they can with retirement visas. You'll likely struggle to find an agent that's willing to work on this type of visa.