Hi Kittie,
Two things occur to me.
The first is that I recall reading on another website somewhere that between 50 to 100 gm of carbs a day is the level at which many people go into ketosis. So you may be lucky and the 83g incl banana may be no problem at all for you. So why not start the BSD with that and see how you go?
My other thought is that as humans we try to anticipate every upcoming issue and solve it before we start, thus making life a lot harder for ourselves than it needs to be. If this is the start of a new way of eating for life, then you know you will make adaptations as you progress. So like Shalimar says, you may decide to go smaller banana, half, quarter etc… But don’t try to impose that on yourself now before you start, just start and then manoeuvre once you are on your way.
I have recently completed the 800 BSD 8 weeks. I started out with breakfast, lunch, dinner, snacks, multiple double-shot coffees. To my utter surprise I finished with only lunch and dinner, no snacks, and only one single shot coffee at lunch. If you had told me this would happen I would not have believed you – and if I had tried to impose those extra rules on myself from the get go, I may have crashed and burned. Amazingly, they just happened, because my body changed. So be nice to yourself, start with the 800 calorie rule, and work with your body from there!
Good luck with the new way of eating, and with the insomnia. I have found that this way of eating has really helped with my insomniac early hours of the morning sessions (maybe the trying to do 10,000 steps a day has helped too). Keep reading, keep posting 😃