I think you'll be fine - my pre op diet is not as severe as the one you have anyway.
Before I even started the pre-op, I'd been low fat, low carb, high protien diet for 4 weeks. Actually lost 18lb last month from when doctor weighted me to hospital weighing me.
They told me they'd have been happy operating right away... so just to continue what I was doing until D-day.
I've been having 80g of natural yogurt (unsweetened) in the morning - make it myself with an easiyo.
Small pack of peas in the pod, butterbeans and edame / soya beans in a light dressing (200cals) from Sainsburys at lunch time.
Snacking on occassional carrot sticks during the day and some protien (normally grilled meat or fish) and some steamed veg (ad-lib) at night