Loyola's Program has always been a three year program. It used to be a POR/PSR-24 program, where one would do the POR at DVA-Hines and then PSR-24 at Loyola. I know that they are in the provess of converting over to the new PM&S-36 model, but I am not sure if they have completed the process or not.
In terms of fellowship, it is probably easier to do the fellowship right after your residency training. This way, the fellowship will not interfere with any job obligations. For example, if you were to work a few years before doing the fellowship and you plan on staying on with the same employer after the fellowship, you will need to make arrangements with that employer to take a year off to do the fellowship. Of course, if you are not planning to stay with the same employer after your fellowship, then this will not be a problem. Right now, I am scheduled to do my AO/ASIF Fellowship in Europe after my residency training. I had to negotiate into my contract with my employer to allow me to take some time off to do the AO/ASIF Fellowship, which is 1-3 months long. Also, doing your fellowship before you start to work will also allow you to market yourself better during your job search. Hopefully, I have answered your question. If you have any other questions, feel free to ask or send me a private message.