2 thoughts -

1. as others have said, it depends on your plan, terrain, weather etc. As a rule, I will always match my kit to my plan, not the other way round (e.g. where are you bugging to, what do you need to get there - no point getting halfway there with a rucksack full of cool stuff)

2. You should be hiking with this pack regularly, so you know your capability, and can build on it. Fitness is task specific, and if you have to bug out, then don't presume you will be able to magically find some extra fitness reserve - I would expect the opposite