Hi lets start at the top and work down.
First that top photo , it apears to be a bit of colapased leave cells ,Its dry so no worries.
2nd photo , The brown spot looks like it was caused by water.If its dey and hard dont worry but you could get a general purpose fungacide and treat the plant.Its caused by water on the leaf for too ling.You might like to increase the air flow around the plant.
3rd photo It looks like the edge of the leaf has been damaged.Again so long as its dry and not wet and hushie you will be ok.
question 1 , Its not normal for plants that are sold like that to need repotting unless its been caused in the shop.The breaking of that root on the underside of the pot shouldn't bother the plant.
question 2, It you do take the plant completely out of the pot,i would suggest that you repot the plant.
questio 3 , answered in question 1
question 4 , The rot could spread but only if the plant is kepy too wet and in tempuratures that are too cold.
question 5 , In repotting the plant ALWAYS use new growing media unless its something that cane be sterilized.
question 6 , I personally would use bark when rpotting but some have good success using spag and others use coconut husk and yet others use a mix of all.
question 7 , Going by the look of the plant the same size pot would be fine.
question 8 , yes