u can stay anywhere in the country during the process, u'll need to go to the embassy in person only if u are requested to be interviewed

You can combine two statements files and present them both. It's fine as long as they're both under your name.

Even salaries as low as 500$ are getting approved so that's not a problem. I suggest presenting a nice portfolio including some screenshots of your online class and your experience in that field to avoid interview asking about your job. And other usual docs such as employment contract, company business license, profile, and recommendation letter.

u can use a hotel booking

You can show more than one bank statement in combination as proof of funds as long as they are under your name.