You don't say what kind of chillies you used, but half a chilli is 1/10th of what the recipe asks for - and that recipe is for a mild dish. You aren't going to get spicy with so little of most chillies.
I wouldn't use olive oil in this dish, either. What the heck are "jammy lemons"?
P.S. It's tikka masala. Marsala is a Sicilian wine.