You need to book flight to apply for a visa to any country.
But just book a fully refundable one if you want to be sure. You don't even have to use that ticket or fly on that date once your visa is approved anyway.
the TM30 can be handled with a simple online reporting system and the 90 day report can just be removed completely. But thai government branches absolutely LOVE their unnecessary paperwork and long queues. So it won't go away anytime soon.
Yes, a new TM30 is needed after every time you come back into Thailand.
Some immigration offices enforce this rule with an iron fist while others don't care at all. But you just need to send a photo of your latest stamp to your agent, so there's no point in skipping it and risking it.