I'd move the money and show statements from both accounts showing the movement into your name and the length of time the money has been in your brothers account.
Just curious, if it is indeed your money, why is it in your brother's account. I think embassy will be suspicious of the real owner of the funds.
Depends on your bank fees for wire transfer and the amount. For my bank, break even point is about ฿150k. Below that wise is cheaper than wire transfer. YMMV.
Always send in your home currency. Thai banks will give you a better rate than your home country.
It is a simple (though sometimes tedious) process. But since you're already convinced, not sure what you're asking about. Use an agent if you want, but use your own money in the bank so you can remove your lips from the agent teat in the future.
I left my Fi data off. Butt then my phone died so now just use Fi web for sms. They won't ship a replacement phone out of the country (not very supportive for a company that offers international service). My Moto Razr died 2 weeks after warranty.