It really depends on whether you want to be a doctor or a nurse practitioner. The safest route is absolutely to stay stateside and complete the NP program, but only you can decide whether or not that will satisfy you. It is a fine and respectable career, certainly, but you will not be a physician. From what I have heard from people on the ground in Lublin, it is not well-organized, and it is a pain in the rumpus, but it is a path to the USMLE and US clinicals and a medical degree. That's what you are paying them for, frankly.
Did you apply to any other medical schools? Jagiellonian still has federal loans, and there are some other E-EU schools that do, as well (although some are 6-year programs). I don't know your stats, but the DO schools in the States would be an excellent choice, even better than European schools with the forthcoming changes to residency numbers.
"When I haven´t any blue... I use red."