Just tell the shop you want 70% for front windscreen, 50% for side and back windows.. Ngam ngam pass

yup, 5 windows is for side windows + back window.
i saw he stated there you can opt for 50%, 35%, 25%, or 5%. so you just choose one of these.
50% means 50% VLT, 35% means 35% VLT (which is darker), 25% means 25% VLT (which is even darker), and 5% means 5% VLT (which is the darkest among the 4).

for your burning question: a lot of cars in msia are doing the same way too. Just that I'm not sure whether JPJ will kacau you or not. Just do the same tone for all your windows which is 50% VLT. Other than 50%, all the percentage mentioned above are illegal since it's darker than allowed % of VLT

nope.. you have to see whether it gives high rejection of infrared (IR) or not~ VLT doesn't affect the price usually.
The higher the % rejection of IR, the higher the price. VLT 50%, but if IR is low (I have checked your link, they didn't state whether how high % is the IR rejection), you will still feel hot with that film.. IR above 70% or 80% would be good as it rejects large amount of heat, but however, if will cause disturbance to GPS and Smart Tag users.