If it was put this way already just consider this revue
Air & Fuel = Fire(temp)
Most of u it sounds like u have plenty of air intake to get hot temps.
That leaves Fuel, are u putting enough hot fuel into your fire basket?
If u want a hot fire, open all air intakes, fill your chimney nearly full.
When good and hot pour onto your cold fuel basket. U should be able
to get over 300* with out difficulty. Now I'm assuming u have the 2"
bung hole wide open.