1) I like to read the whole thing once over to form my own general opinion of the novel, before I go into textual analysis. It's important to remember that the two should never be divorced completely because you want to be an alert reader, but that's my general strategy - forget about having to pick it apart
and just read the damn thing. This also helps hugely come write-up time because you usually have a much better picture of where the key passages/scenes that you might want to use are. If it's a good book as well (which ,I'm sure everyone knows, prescriptions are too often not) you'll thank yourself for the enjoyable experience as well. If you don't like it, this way you'll probably still gain a begrudged appreciation of the text's construction.
2) Once completely (see above), but always come back to the text. If it helps, make a sort of rubric where you can systematically identify key scenes and do a bit of concentrated exegesis on each section, so at the end you have a macro-level analysis and a micro-level textual support (as well as a good understanding of how those intersect).
3) How many hours did you spend on the subject?
Quite a few, but I didn't slave away at the subject with a fixed schedule. Whenever I found/thought of something interesting, I'd work on it a bit, whether that was an idea for a new creative or a line of inquiry for a thesis about the module. I tend to be of the opinion that good writing comes when it comes. If it won't come when you want it to, it's probably not there at that moment. That being said, a lot of shit writing does very well at the HSC, so I suppose if you just want to develop some skills like the employment of techniques, whatever whatever, go ahead. It probably won't hurt you.
4) Yes! Constantly reading new things (both related and unrelated to English) is a good way to grow as a thinker and a writer. It's a good way to develop skills and usually exposes you to very interesting writing which you'll be thankful you read. Read widely too - from poetry to journalism to short stories. Follow lit mag pages, podcasts, etc. if you're lost as to where to look!
5) Keep reading, and think about what you might want to produce. This will probably change, but unless you go into Ext 2 with a burning passion for literature and/or film, you'll fizzle out very quickly. You shouldn't be alarmed by this because it's probably the exception, but I wrote almost all of my work in a hyperactive frenzy during the summer break between Term 4 and Term 1 (a lot of it was rubbish and I spent a lot of time editing it in Yr 12). But I suppose in an anecdotal way that's the level of commitment you should have to your work - because at the end of the day, it is your work.