Hello,
Honestly, there AREN'T that many resources available for Computing subjects in general.
http://vceit.com/ would be your best bet in terms of reliable resources.
Missing Unit 1 won't impact you, if at all. It's not one of those subjects that heavily relies on Unit 1 and 2 to do well in.
VB is a terrible language, I agree. Your school should be adopting Python, really. It ticks all the boxes in terms of easiness to learn, object oriented (satisfies the requirements of SD) and is freely available/cross-platform. JavaFX on the other hand, is not that easy.
But kudos for understanding it, it sounds like you'll do super well.
In terms of scoring 45+, it's absolutely possible to do this. You have a natural interest in the area given your experience - I can tell, so that definitely will help your situation greatly.
Programming itself is only half of SD - you have to bite your lip through a ton of dry theory (e.g. problem solving methodology application) as well. Enjoy
Cheers!