Funny enough I just had the same, from Jomtien. It's my first 90-day report since returning from a long weekend in Penang. As usual I did it on-line. They rejected it because my first one after returning has to be in person.
1. Address doesn't have to be permanent, as such. A one month booking a hotel will confirm in writing will suffice. It also gives you time to look around.
2. After one night, ask hotel to confirm they've done TM30. Take the booking confirmation to Immigration to get a Residency cert.
I agree that is possible. Depends in the IO and the officer on the day. If the OP is changing the method to monthly and can show they meet that requirement, and have done for the previous 12 months, then I think it is worth a try. Worst case scenario is they again use an agenth
If you have no choice but to use an agency this time, ask the IO exactly what evidence they need of your income of 40k a month and make sure you can provide that evidence next year, to avoid the agent's fee