2. Yes you do.
3. Prices are the same as in the games and items will be determined by your amount of badges. I will say right now the shops will only give Potions each for 300 and Pokeballs each for 200. You can earn money from beating trainers and selling rare items.
8. If you get a Pokemon with Pickup, you can find rarer items more often depending on the levels. Just finding items, you won't trip over a lot of them but you may find more berries on the routes and manmade items in the cities and towns. Picking up TMs will likely happen more on the pathways and at Pokemon Centers.
Nideous, that's perfectly fine the way you've done it. Leave it the way it is.