Hi mate - welcome & nice choice of car :)
I don't have answers to all your questions but will help on the ones I can.
2) I believe from the factory they have W rated tyres.
4) Falken FK452, Toyo T1-R, Goodyear Eagle F1 are all alternatives, however the Vredsteins & Michelin PS's get good feedback on here.
5) Yes for the belt, also the water pump whilst your at it (dealer will do this extra for just the water pump part cost only not labour when doing a cam belt & tensioner change). And yes I would change the fuel filter every 40k at the very least. It's a very easy job on these cars - part number for fuel filter is 1K0 201 051 C
The DV is basically a precautionary change, it's worth just buying the latest revision 'D' valve part number is 06H 145 710 D
7) No way! Not many people tend to care much for the ICE, but for me it was the first priority! The stock HU is pants, a lot of people tend to upgrade to the RNS510 which is a factory fit, touch screen factory look stereo with sat-nav built in, looks great, but the sound quality is debatable, as the amp isn't a great deal better than the other stock stereos - subjective as is all ICE opinions.
I swapped my stock HU out for an Alpine CDE-114BTi - this offers bluetooth calling handsfree syncing of a phonebook, voice dialing etc, it's easy to wire in, and if you buy a CAN-BUS adaptor, you can use your existing steering wheel stereo controls (if you have MFSW) to control the HU too. The sound quality is good even with stock speakers, although I personally bought a small Alpine AMP/SUB combo to put in the boot. The HU was about £170, Can-Adaptor around £35 & Sub around £130.
The sound is FAR far better than it was, but I think the other speakers will need replacing to something half decent, even a decent set of Pioneers or JBL's would be a major improvement.
Of course you could fit the RNS510 and then amp it up, which would give you the best of both worlds.
But if you plan on using a handsfree phone, you've then got to shell out for a VW Bluetooth install or Parrot kit which is more £££ on top.
I will 100% say, that if you buy an aftermarket stereo, buy the original VW fascia panel to allow single DIN stereos, it gives you a storage tray underneath, it absolutely does NOT look as good as a factory fit stereo like the RNS510, however the cost difference and sound improvement outweigh this... In my view.
8 ) Best to use Tesco 99 or Optimax, others im sure are fine, but it tends to be the BP & other SUL fuel are more expensive.
Any other questions mate feel free, we are a helpful bunch on this forum :)