Welcome, H9!
A) On a good day - trafficwise that is - your definition of Brussels area covers quite a lot of our country ☺. If you plan on flying in the weekends , you will have a number of options. I fly (gliders) at EBBT near Antwerp which is a former military field in beautiful surroundings. The resident flying club owns a diverse fleet (ps28 Cruisers, C170's [one with glass cockpit], Piper Super Cub's and ULM's)
B) There are some syndicates around, but I don't belive many spare shares are advertised as they are in the UK. More of a word of mouth thing. I believe on our field there was a share in a Pa18, but I don't know if that is still available. Depends on what type of flying you are after. The rate of 180 seems quite steep. You should be able to do much better than that at most smaller fields.
C) Our field is only operational in daytime so the night rating could not be used. Perhaps flying clubs on larger regional/international airfields (Antwerp, Kortrijk, etc.) do have that option.
D) and E) An easa PPL should be acceptable in most places. If you want I can put you in touch with people more versed in the regulation of (motor)flying in Belgium.
Good luck and hope you get to experience our lovely yet deliciously complicated airspace!