transfers to foreign banks are always converted to the local/receiving currency unless the local bank account happens to be a foreign currency account.
An employment letter is if you work for a company, but you don't, you're a freelancer. Suggest you put on your thinking cap and prepare yourself to write a cover letter to present yourself and your portfolio to the Ministry of Foreign affairs for your DTV Visa.
No issues, you can also do the crossing at Sop Ruak at the Golden Triangle immigration office, that takes you by boat across the river into the special economic zone.
You should be okay but be prepared to maybe spend a day or two outside of Thailand before being allowed to come back especially if you leave and return by land border.