Hi!
Much of it was already written in previous posts and maybe I'll somehow repeat them, but nevertheless:
1) pillow: I'm used to sleep with a quite thin (but wide) pillow and didn't experience any trouble with that on the Camino. Whether they had one (usually very bulky) or not. In that case I've made me one with my fleece jacket, T-shirts etc.
2) drying shoes: well, try not to walk in the rain
, kidding. Hospitaleros are very well aware of your problems when arriving to the albergue due to the weather or else and you can count on that the solving of the trouble has been already done in a way (fireplace, central heating etc.). Stuffing newspaper sheets in them also helps a lot of course.
3) spiritual preparations: I've done none whatsoever. Maybe just some thoughts of being away for a month and a half from my beloved. The Camino itself is a spiritual journey (as well as physical). But since I'm not a traditionally religious person that might just not be enough of an answer for you.
4) jet-lag: my experiences with jet-lags are very limited (EU-Australia), but I would either try to sleep as much as it is possible or as little as I can. In the meantime you forget your home time and upon arrival just do everything as if you lived in EU for decades.
5) married, young couple: mostly I've walked alone but in the second part of Camino I could say I was "involved" with a Spanish peregrina
So - when walking try not to be "glued" to each other especially if you have different pace of walking (uphill/downhill,...), sometimes wait for each other and offer some help as you would do for any other pilgrim, listen to yourself and your companion, make compromises because three days later you might need one, but in the evening it is very nice to be together and talk, cuddle or whatever
Also take a private room (app.25-30€/night on the budget) especially on the rest-days if you're planing any (but do that, maybe in larger cities as Pamplona, Logrono, Burgos, Leon, Santiago - depends on whether you like more urban or countryside atmosphere).
Buen Camino!
And hope to hear about your experience