Troubles with quinoa consistency
Quinoa is cooked much like rice- in fact it can be cooked nicely in a rice cooker.

The 2/1 ratio is correct. As with rice, the goal is to steam the grain. You should be cooking on low heat after it boils and is covered and you shouldn't be frequently opening the pot while it cooks.

I haven't had success adding water later in the cooking. It doesn't get a chance to turn to steam and instead just boils the grain to mush.

As with rice, some of the quinoa might stick to the pan, especially if it was cooked a little too hot or with uneven heating. This isn't necessarily a bad thing. With rice and quinoa I like the crispy bits.

Adding oil late in the cooking probably won't help you achieve the desired fluffiness.