I like how you make H2 burn hotter than O2, but I have a better idea, that should probably be implemented before someone makes a save using this that would become broken if my idea were implemented.
I think H2 should by itself burn the same temperature as O2, but when mixes (such that burning them together makes steam) that then and only then the flame should be hotter.
I found H2 burns at about 1200 by itself O2 burns 800. 1200 is hot enough to melt metal. 800 isn't. Now the ONLY time it should be hot enough to melt metal is when the H2 and O2 are mixed.
Hydrogen (H2) air 2210 Hydrogen (H2) Oxygen 3200 List of burn temperatures through testing. That is why I made the temps equal to that, though there obviously is a glitch somewhere if the temp is lower than that.