when i was in the market for a car, kasama din sa choice ko yung MS. but i chose the forester over the MS becuase the MS interior just feels so cheap and the ride isn't great also. try to test drive both and see which you prefer, also have you looked at mazda's cx-7? grabe ganda, sayang wala pa cx-7 sa philippines nung bumili ako ng car.
to answer your questions:
1) yes, compared to the XT it is very underpowered kasi naman XT has the wrx engine in it so it is fast. compared to a tucson, don't know how much difference there is since i haven't driven a tucson yet. pero compared to regular cars we see in our roads daily, hindi naman siya under powered. and my car before the 2.0x is an 05 STi, and driven lots of fast cars, so i can say that it is not underpowered compared to regular cars on the road we meet daily.
2) 5-8km regular FC of the 2.0x, that's because of the awd so that's one of the downsides besides being underpowered.
3) subaru only makes one of the best AWD system there is, only audi can match up to it's AWD system.

search for subaru awd on youtube and you'll see how good the AWD system of the subaru is. you'll even see an STi pulling a 40footer truck out of an icy road.
4) parts are a bit more expensive compared to other japanese cars, but not that much.
5) all subaru's are equipped with HID.
6) what do i love most in my 2.0x, it feels like i'm driving a car not a CUV. also even though it is "unerpowered" it makes up for the handling, handling is very great especially in the twisties and very very stable at 190kmh.
if you can get the XT i suggest you do, the difference in performance is just to big. when it comes to performance no asian CUV/SUV can compete with the XT. the combination of handling and power of the XT is just truly amazing, plus the potential of the XT's engine is also amazing. can you believe that with just a full exhaust, cia, and ecu tune the XT will be as fast as the STi.