Hi, if i do the calculations:
1st yr GPA: ((4.5 x 7) + (6.5 x 1))/8 = 4.75
2nd yr GPA: ((4.5 x 2) + (7 x 1) + (6 x 1) + (7 x 4)) = 6.25
3rd yr GPA: (7 x 8 )/8 = 7
Weighted GPA: (4.75 x 0.2) + (6.25 x 0.4) + (7 x 0.4) = 6.25
So the "Maximum GPA" that you can achieve, seems to be, 6.25, and that is assuming you get H1s without missing a single one.
Also, according to the PagingDr's 2018 medicine offer extract, you need this 'combo' score of 1.6 (which is a theoretical number, so there is no evidence to support whether this is accurate). But, since this extract uses real data from applicants it shouldn't matter at all. This is calculated by (GPA/7 + GAMSAT/100)
With your current GPA; 6.25, and assuming you need a minimum combo score of 1.6; (1.6 was the lowest average of combo score)
6.25/7 + x/100 = 1.6
x = 71
So to have 'some' chance, you need a GAMSAT score of 71 (Which is high for most medicine applicants in the data)
This high GAMSAT score is to balance out your 'low' GPA. (See my attachment below). The lowest average of those offered a place was 6.23 (Flinders uni), 6.14 (UniSyd), 6.26 (Uni of Wollongong).
Which means you have a chance in those unis. However, University of Sydney mostly looks at GAMSAT scores if your GPA is over 5, and their average for GAMSAT is 71. Wollongong is a portfolio university, so if you did have any life events that impacted your study, or have any volunteering experience you may have a better chance at these universities.
In my attachment 2, (GAMSAT avgs) you can see that average gamsat shows an upward trend, implying tougher requirement for application processes in the future. Hope not

As for University of Melbourne, they have a GPA average of 6.69, and a GAMSAT average of 70.09 giving an average combo score of 1.66. So, I'd say you have a small chance of getting an offer at this uni. However, any uni for medicine is good and won't really make a difference to your qualification.
I wish for your best

I'm wanting to get into medicine in the future too.
Hope this helped
P.S: As for DDS entry, i am not sure but i remember entry requirement being similar but without the interview hurdle.