(Never rode long distance, I am a newbie, but I lift in the gym regularly for 18 months, so consider this a disclaimer
)
Peanut butter is very very calorie dense (100 grams is 700 calories, a "bigger" [but still compact...] tub is 470 grams i.e. the most dense palletable food I can think of, space wise especially, unless your into drinking olive oil
)
A cup of tea will make it easier to eat, but I only find myself *needing* a drink if its more than a table spoon of PB.
The sugar element will provide quick energy, the fat (of which is around 85% I believe) will satiate well, good food before bed to burn through the night, so you don't have to eat within an hour of waking up.
This is anecdotal (from me at least) but Im lead to believe omega 6 (vegetable based oils/fats) should be balanced with omega 3 (fish) - but no one is going to match the two with casual diet adjustments (you'd have to eat fatty fish every day), so perhaps take a small tub of concentrated cod liver oil tablets, and neck a capsule with the PB.