You can apply while in the USA - you cannot apply in Thailand so if you did come here you would then have to leave to apply in Vietnam, Laos etc. The same is true of applying for the dependent visa for your kids. Much easier for you to apply for all of it in the USa and arrive with the visas
Have a quick search in the group. There have been a few posts recently about successful applications in the UK with the money not requiring seasoning for 3 months.
Decide where you want to stay before signing a 1 year contract. There,are shorter terms available. Of course you could get Ed if DTV rejected but from everything you have said I very much doubt it would be rejected. You seem the poster candidate for soft power :-) I would not worry. Try and few locations first on the 90 day visit to decide where you wish to stay ie city, beach, islands, countryside.
Jomtien have changed their minds backwards and forwards a few times that I know. Wanted it, then chased away, wanted it after travel, chased away next time lol. At least in Chiang Mai I know 100% it is required after overseas travel. I need to check for domestic travel. Luckily I just message property agent when I return and she does it and sends me the acknowledgment.
I think it will depend on how closely they look at the application. Organising exhibitions etc in Thailand itself would seem to be outside the remit of the DTV as you will have to deal with Thai companies, organisations and people in Thailand. Good luck and hopefully they do not scrutinise your statement too closely.
But the immigration have your record of leaving the country. Whatever, there is no need to show a TM30 when entering the country. I think yiu are totally misunderstanding what the TM30 is. Just forget about the TM30 till you reregister. You are both overthinking and over complicating matters.
You can show a hotel booking but that is not a TM30. A TM30 is registered within 24 hours of you arriving at accommodation. A hotel cannot register you till you check in. The TM30 you had is not valid now.