Don't do anything now. If your attending is doing this stuff now, he won't stop (and will likely get worse) as times goes on. If you really want to do something, document as much as you can whenever you feel something is shady (patient info, details of the situation, dates of patient care etc). Make sure they are your patients as well, so you actually can access the medical records without it being a violation. Don't report anything until you have graduated. This is important for two reasons:
1. You want to be as far away from the situation as possible if you're going to report him, so no possible repercussions against you if he finds out it was you.
2. The more training/education you undergo throughout your residency, it is very possible that some/most/all of the "violations", weren't actually violations rooted in greed, and there was actually sound reasoning behind the decision making.
"Patient has a stroke, MI, trauma or something else that needs transfer to a tertiary facility that has stroke center, cath lab, trauma center. Attending doesn't want to give up the daily billing and refuses transfer." - Maybe the attending feels comfortable handling management of these patients and has a solid track record with these type of patients without transferring. Maybe he feels that transferring these patients 20-30 miles away isn't worth the inconvenience to the patient's family and friends who wouldn't otherwise visit the patient daily to offer support. Maybe he has dealt with issues with insurance companies that can be really difficult in these situations. Some insurance companies explicitly state that if you go to through the ED at one hospital, but care is transferred to another hospital, they may not feel the transfer was warranted and the patient can end up with some absurd bill from the second hospital. Maybe there is a push from administration to keep these patients (and care for them properly) so that your current hospital is recognized as a top-tier facility that has the resources/specialists to handle complex cases). Most of the billing for inpatient care goes to the hospital anyways. If patients are dying left and right because they are not being transferred that's a different story and more concrete, but that does not seem to be an issue.
"Patient is not stable for discharge per some specialists, but patient's long term care facility is afraid of losing patient so attending discharges unstable patient anyway." -Every hospital and insurance company pushes doctors to discharge patients as soon as possible. That's just the reality of medicine. Theoretically, most patient's aren't really 100% stable from every specialist's point of view who has seen them. Everyone can benefit from a day or two extra in the hospital to completely ensure every vital sign, lab, bodily function is completely normal, but thats not the reality of medicine. Insurance companies can be ruthless when it comes to not paying if they feel the patient did not need to still be there.
Wait until you have graduated and see how you feel about everything you witnessed and documented. If you still feel a type of way about the situations, turn over the info to the proper people (Insurance Panels, Medicare, State Licensing Board, Specialty Board), and move on. In the rare event, he knows/suspects it's you, you will be gone and he won't be able to touch you. In addition, so many residents will have rotated through his service, he won't have a clue who dimed him out. At the very least, if there are no concrete penalties against your attending when the investigations are complete, he will likely always be looking over his shoulder and go legit as possible.