I noticed from one of the earlier pics that you posted that the gas burner was being used to heat the oven.
I have a "pre cast oven" made by Pappaz Ovenz in South Africa, and it is also a wood/LPgas burning oven. I have found that the gas burner gets the oven to very high temps (950 deg F) within about 20 minutes, and I can then cook a pizza in under 60 seconds. I start the heating process with wood, and then "boost" the heat with gas, and cook with both heat sources burning.
Have you found the same ?