Sounds fun! People will have their own opinions on the various trails, personally I wouldn't rush to the Great Glen Way but as part of a bigger trip I think it would be a great idea.
I think you've got the right idea though, I'm constantly delighted by how much more of Scotland there is still to see, I've just cancelled a trip to the Alps (financial reasons) but think I'm actually more excited by the 'budget' alernative of 7 days on Skye
You should absolutely persist with your plans though, once you're more confident the biggy awaits - The Cape Wrath Trail!
Your choice of trails is sensible though, mostly well signposted, relatively well trodden. I wouldn't be expecting many campsites still to be open in November though... Some hostels would be though, Crianlarich and Glen Nevis are year round last I checked.
Ben Nevis in November could be interesting though, lack of light, god knows what sort of weather, definitely demands a good idea of appropriate clothing and knowing if conditions (snow and ice) are perhaps beyond your abilities.
The simplest safety precaution (and the one most likely to reassure your mum!) is daily, or at least as regular as possible, call ins. It's important to recognise lack of reception and possible battery issues with your phone, so perhaps plan to call in wherever there is a phone box (think they're usually marked on maps, most hotels will have one in the lobby as well). If you do injure yourself, you will be carrying everything you need (tent, clothes, stove, food) to survive for a few days until you're missed, and hopefully someone will know your last know location and intended destination.
I don't pack a crazy amount of 'extra' food for most backpacking trips under a week, although yours would be longer than that. Having said that, you'll be passing through enough towns and villages to supplement whatever you're carrying (with chips mostly!).
A rough daily allowance for me would be:
Tea/coffee and a large Stoats porridge bar for breakfast, maybe a satsuma if I can be bothered carrying them.
Lots of snacks during the day, fig rolls, nuts, jelly babies, chocolate
Lunch - a mixture of oatcakes, babybells, salami (take a whole one and chop hunks off, looks manly and tough haha!) or maybe even a couple of mini pork pies, if I can be bothered carrying them
Dinner - A Tesco cous cous with some olives/feta tossed through, dead simple and cheap. Alternatively pasta and pesto (be VERY careful how you carry the pesto, a screw top tupperware flask in several baggies seems to be the only way).
Dessert - More chocolate, hot chocolate/tea and or whisky.
You'll know yourself how hungry you get, personally I almost have to force myself to keep eating at times, little and often is definitely the best strategy.
Loads more stuff but I'm sure others will fill in the gaps!
