Hi there
I may be able to offer some help.
It is not easier to land an internship by being Australian trained. You will be just as likely to miss out on internship opportunities if things progress as it has and the government continues to fling around the responsibility of internship sponsorship between federal and state. There is most definitely no guarantee of you becoming an intern especially with how competitive places like Victoria and NSW are. You will likely be thrown to Queensland, WA or Tassie if granted a place but it's more likely that you'll just be asked to leave the country if you can't get an internship in the state you went to med sch in. This applies to all schools. The only school that kinda "guarantees" a spot for you in its home state is ANU where rumour has it a spot in ACT will be catered for its graduates but only if they do not apply anywhere else (check up on it).
I don't qualify for Monash and it isn't recognized in my home country so I haven't done much research on it but I can safely say that there should be at least a couple of weeks (4-12) that you can do international electives. This allows you to apply for clerkship in the US schools for the much needed USCE (US clinical experience) which is a huge boost during your return application as an IMG. USMLE prep is also self-catered ie: no one's going to help you do it; you're going to have to do it yourself irrespective of institution.
Going to UQ-O actually disqualifies you from getting a residency spot in the entire state of NY (which is a pretty big deal seeing how many IMG friendly residency programs are in New York), as does doing more than 12weeks of clerkship outside of the country of your medical school (UQ-O is counted as having 2 years of clerkship in the US as the med school is in Australia). If I remember correctly, there is also no additional/special time allocated for you to study for the USMLE aside from the bare standard that most other schools give. To my knowledge, the only school that actually bothers to specially cater for American (or aspiring Americans like myself) students is USyd which gives you 2 months to prep for step 1 and even allows you to postpone a year 2 module to year 4 for even more time to prepare. That's on top of having the most elective time and allowing you to do a core rotation (med, surg, etc) at an American institution which really racks up your USCE. It's pretty obvious how USyd is the way to go (if you can make it in) if you intend to return to the US.
Transferring among medical schools require extreme circumstances usually relating to ill-health of a loved one where transferring to the institution will allow you to provide better care or stuff like getting threatened, raped, discriminated against in the previous medical school. Otherwise, it is extremely unlikely that such an application will succeed. Also pretty sure that UQ-O is a special program that will not allow students in after its start date. If you're talking about traditional UQ, there might still be a faint chance but if it's UQ-O, I would say you have 0 chance.
Regarding the comparison of tuition fees, we must really remember that it's not only limited to tuition but overall living expenses. A school may cost 3k more per year but may be based in a location with significantly lower living expenses. That's the case between UQ and Monash as the former is in a relatively cheap area (Brisbane) whereas the latter is in one of the most expensive cities in Australia (Melbourne). Of course there are also oddballs like ANU where the tuition is not only the most expensive in the country @79k, the living costs in Canberra are also second only to probably Sydney. Don't get me wrong though, it is still a solid program; just that the cost of studying there is astronomically high. Remember to compare such costs in context and don't pick a school simply because it is slightly cheaper. Pick a good school because the difference in tuition fees will be laughable once you start working