lol ok, big list so here goes
Xr2i loom is fine, doubt the Xr has pas so if you want pas you'd want to swap for a 16v Si loom as most had pas, yes modifications to the loom for a cvh
guide for the plug changes are 2/3 of the way down the page
interior loom will remain untouched
2fdc is pre pats and your and every Si is post pats, and these are not interchangeable! so you need a word coded ecu, Deep, Desk, Dewy are all 2.0 ones, they will work yes but mk3.5 RS1800 Cult ecu would be ideal, but these are very rare, 2.0 ones cost about £60 as it is
(as a rule most post pats ecu are an actual word rather than a jumble of letters and numbers)
(as another rule, for odd reasons mk3.5 fiestas had the immobiliser/pats built into the car, NOt the ECU so changing the ecu wont effect the pats, but mk4 and there after fiestas have pats in the ecu, changing it removes the pats opperationg unless you also keep the original key for that ecu)the escort inlet can be used, although it can be a bit hard to work with as its very tight fit in the fiesta bay, power gains are very sceptical, but i believe them to be worse than the H.O inlet
S.o is fine but obviously less powerful/more restrictive
the xr2i injectors would be fine to use, might hamper you if you went for more power like say 150bhp but be fine for 130spec
2.0's use brown injectors, not sure on the RS ones but they may be the same as the 2.0
RS turbo ones WONT fit, theyre very different and the ecu would likely be confused by them (different impedance and Ohms)
CVH rear engine mounts are different, but i believe they fit a zetec with modification, i also believe some CVH mounts are stiffer than zetecs, if not all of them (due to the zetec being designed to be more refined)
for changing to non PAS you will need a non pas union for the bottom of the column, they have a different sized hole that fits the rack pinion, i believe the non pas one is larger (or smaller either one)
id strongly advise you find either a 1.6 Si, RS1800 or Xr2i (16 or 8v) gearbox
when i converted my 1.3 mk4 to the 1.8 zetec the gearbox was very short, juddery, slower in both acceleration and top speed than the same engine with no other work done, whist fitted to this Si (Si was positively quicker in acceleration, and where the mk4 could only reach 126mph, the si can reach 132mph)
plus its likely to last longer due to the added power (myth)
zetec flywheel is fine even in the cvh gearbox (or even HCS gearbox)
LSD will fit any BC gearbox so yes it will fit your 1.4 box
most of my answers ive actually done and tested myself

some others could be argued haha