No it should not cost you anything because they should have already submitted the tm30 on your arrival as it's thai law. That being said if I were you I would have a chat with them first if you are wanting to extend your stay with them? If not then book yourself into a cheap hotel and they will submit a new tm30 for you and you can get a copy and use that for your extension
No need to apply for a visa. You will get a visa exemption stamp for 60 days which you can extend in thailand for another 30 days at a local immigration office
the DTV is for both individuals who work remotely i.e. work in thailand for a company other than thai and for a number of soft power options I.e. muay thai boxing , appropriate cooking course agreed with your thai embassy where you apply and a few others.
Peter i agree I think the website is incorrect for a non O. Worse case is you upload flight details of a real flight without booking the ticket. The airline should not be interested as it's a long term visa to see any out bound flight