Welcome,
1, as above
2, picture looks standard to me, what do you think is missing?
3, as above, anti corrosion stuff, nerwer cars seem the get dipped in them they chuck that much on them haha
4, mpg depends how you drive it, but 12 seems low, Are you running it on vpower/99? does it have any mods bar the dumpvalve? can you get it on a rolling road to find out whats going on?
5, rusty bits are pretty normal
6, Regular oil changes, 3k or 5k depending on how you drive it, if hard more regular changes. Always keep on top of maintenance, running it on decent fuel 99 ron. If theres an issue (eg stutters on power, check engine light etc etc) dont try to drive through it, get it checked out.