As long as you can prove leaving the country it’s good. But it’s ONLY the airline when boarding that will ask for that anyway. Once you hit Thailand you won’t be asked.
Unlikely to succeed on income. Got the other route if you can and do a verified course that gives you the visa, yes it costs money but much easier for you.
check with the relevant embassy, it really does depend on if they can read the documents or not. And English is accepted everywhere as the primary business language hence it’s used in other places.
Maybe an oversight by issuing officer. But the account has to be in your name as well. Not even sure joint account is accepted, certainly not for visas in Thailand.