A lot incorrect information in this video when it was released a while back. No one in reality registers a guest with immigration when they stay overnight and the email address given is invalid. Also yes if you are a long term resident or owner then you are the housemaster but legally when renting, the Landlord must register the TM30. Very confusing the whole.TM30 deal.
You said you have booked long term. Do you have a contract with the owner? If so you can lodge the TM30 application yourself and do not need the owner to be involved at all.
Keep using 30 days until they stop you. Otherwise no limit. It is more of a problem if you do it back to back without any breaks in the middle. Hence why Oil and Gas workers get away with it on a 28 and 28 or similar.
Correct 8k AUD or equivalent. Not really ridiculous for staying 6 months or more in Thailand. Works out as 33k a month. If you have the money in the bank it is no big deal. But you also need flight tickets and accommodation details as well.