Showing income deposits is a requirement for many embassies to get approval. Requests for pay slips, and payment of services are common as many posts show,
It is not a problem. You can come and go as you please, the DTV is a multi entry visa. You could mention in a cover letter your return home in April and then returning to Thailand to restart your training
Should not have any probs, as you are going back to your hometown. The rules are focused on the border hoppers who are staying long term in Thailand without a visa to cover their stay.