Good luck! I am sure things will turn out well for you. The train to SJPDP is pretty easy, as others have pointed out. I arrived about 6:30 pm and stayed in SJPDP that night.
The pilgrim centre can be busy and it might take 15 minutes or so to get the credencial and find a place to stay. Personally, I would not walk to Hunto that night. Relax, get your gear set up and settle into the camino routine. No point stressing.
My pack was less than 7.5kg. The key thing is to be ruthless - and also to cast aside vanity. By vanity I mean that a man does not NEED to shave, so don't take shaving gear. Ladies don't NEED facial cosmetics, so leave them at home. I normally have very short hair, so I did not need a hairbrush. Men may want to consider a "Number 3" haircut like mine and leave all the hair grooming stuff at home.
It is certainly good to do at least one training walk of say 20km with the actual stuff you will be carrying, including water and food. I did a couple of these and weeded out items each time.
On training walks, unless you are an experienced walker and know your body and its capabilities, try to do one walk of the distance you plan to cover in one day, say 30km. In my case, the optimum for me on the Camino turned out to be 25 - 30 km/day, with one day of 42km. One has to pace oneself for the 30-day journey and certainly not try to keep up with companions who may have a faster pace.
The thing is that a heavy pack might seem OK at home, or after one training walk. But it is different thing to carry that pack for 30 days over all kinds of terrain. The aim is to maximise your chances of completing the camino without injury.
Re animals, I never had a problem. You see quite a few dogs with sheep, but they were OK for me.
I hope this is useful.
Bob M