Hi!
1) the bike will be fine.
2) I suggest ortliebs. Good mounting system, no raincovers, you can even swim over rivers if you need to and keep your stuff dry. they aren' t so expensive in europe as they are in US. You can find them used now and then for a good price. (i got my first pair of back packer classic for 60$)
3) tyres depend on your route. If you will ride mostly on asphalt, i would say you will be happy with 26x1.5 or 1.75 at most. Anything wider will slow you down. Continental Travel Contact or Schwalbe Hurricane (if on tighter budget) would be my choice. they are good all around tires.
5) either put the butterfly trekking bars or add some bar ends to your straight bar.
6) I would say something from brooks, but if you dont want a leather seat, specialized makes good saddles. You needsomething that is not too wide and not too soft.
7) add some allen wrench kit.
8) maybe try to change a spoke.
10) stick with cycling.
11) Don' t leave your stuff alone.
14) Cycling clothes aren' t a necessity. You need at least 1 set of clothes that dry fast. Clothing should be comfortable and thats the main thing.

good luck!