Problems with creating sodium hydroxide from sodium (hydrogen) carbonate
You are correct: Taking baking soda and heating it to $850~\mathrm{^\circ C}$ will generate sodium oxide and liberate carbon dioxide and water. To generate sodium hydroxide, all you would need to do is wait for the heated soda to cool down and then add water. Beware! The reaction of sodium oxide and water is strongly exothermic. React the two carefully!

A red-glowing spoon is a certain indicator that the temperature of the flame was larger than $500~\mathrm{^\circ C}$. A blue flame is usually an indicator for complete combustion. In the context of bunsen burners, that is typically larger than $1000~\mathrm{^\circ C}$. I cannot say whether your gas flame reached that temperature or not.

Note that once you have created sodium hydroxide you should handle it carefully. Especially do not attempt drinking it and keep it off your hands. Proper safety equipment (goggles, gloves) would be preferable.



Concerning the industrial process, the question is usually not so much what the problems with a certain method are, but rather what the benefit of a certain method is — especially if that benefit relates to cash. Electrolysis of a sodium chloride solution is a very cheap process with sodium chloride and water both available at almost no cost and electricity also typically cheap. Acquiring sodium carbonate is probably already more expensive than the required sodium chloride and heating to $850~\mathrm{^\circ C}$ is certainly much more expensive than letting a current flow through the solution. Hence why the chloralkali process is preferred in industry.