Updates:
Manage to apply some decal last night, from 50cm away it looks ok
Close up of the damn brittle decal

it crack before i even apply Softer, and crack even more after i apply softer, now i need to mix some fluorescent yellow and hopefully can touch up those crack lines, other part where decals sit on flat surface was ok
Side door decal gloss coat, after few days, wetsand with 1000 & 2000 then compound with Autosol, Tamiya Coarse & Fine Compound
here's the gloss coat without wetsand and compound