Are the forms for the one-year extension of a Non-Immigrant O marriage visa the same as the original application?

The actual form is the same, but there are more documents you need. You need copies of everything from before plus your rental contract, if you rent, with a copy of the actual owner's ID card, and a copy of the house book he is listed in, and your lease with the address. If it is your spouse's home then a copy of their ID, and copy of the house book they are in, with letter stating the living situation, and that the current TM30 matches that address. New bank letters, and new picture. Save copies of everything as you just need new bank letters, and new pictures the following years. Oh, and they do compare pictures to make sure they are new. It all gets digitized.

Depends where you got your Non Imm O from.

Yes except the money in the bank needs to be seasoned so if you got your Non-O in country and haven't touched the funds you will be fine