1) Dont worry we wont talk about ur 2.0D and yes it can take to places even where HONDAs wont go 
, as far the springs are considered , common brands available such as MAXSPEED will do the trick , they would drop round about 1.5" and the car would look good as u have added 17s (keep in mind they would be a bit stiffer than OEM ones)
Only adding springs wont fulfill ur adjustable query so if ur looking for anything that u can adjust then add a complete set of coilovers i.e height adjust + stiffness adjust , if u only get Adjustable shocks (NOT having stiffness control) then they would be even stiffer than only adding lowering springs
2) Well u can talk to ur mechanic regarding it , people usually get complete rear end with shocks and coilovers for a conversion , i hope the JDM swift suspension would be a good replacement
3)If its manual then go for 16" size rims max , it wont harm ur fuel economy that much , wont interfere with the ABS and have better grip and wont harm ur suspension unlike 17"/18" . Better add branded 16" rims + 205/55/16 or max 215/55/16
Thanks !
The only usual way to lower on stock suspension is to cut the original springs that is NOT advisable
