I encourage you to make the move to Master Unlimited. Studying and taking the exam is easy enough for a man with your background and ability. You could get Master AGT without STCW, and then add the STCW later as you can find time and money to take the required courses.
Hopefully, as more schools get approved to offer the new STCW courses, prices will start to come down. I wish the USCG would let us take foreign STCW courses. I have no doubt that most foreign STCW courses would be much higher quality and much much cheaper than US courses. Besides, it would be nice to be able to write-off a trips to Italy, Croatia, and other interesting places.